diff --git a/src/manywidgets/_base.py b/src/manywidgets/_base.py
index ba94384..e912389 100644
--- a/src/manywidgets/_base.py
+++ b/src/manywidgets/_base.py
@@ -28,6 +28,21 @@ def _next_id(prefix: str) -> str:
         return f"{prefix}_{_id_counters[prefix]}"
 
 
+def _flatten(children) -> list:
+    """Flatten one level of list/tuple args into a flat list of children.
+
+    Lets layout widgets accept a mix of widgets and lists of widgets, e.g.
+    ``Column(slider, binders, m)`` where ``binders`` is itself a list.
+    """
+    flat: list = []
+    for child in children:
+        if isinstance(child, (list, tuple)):
+            flat.extend(child)
+        else:
+            flat.append(child)
+    return flat
+
+
 def asset(module_file: str, *parts: str) -> pathlib.Path:
     """Resolve a path next to a widget's ``widget.py``.
 
diff --git a/src/manywidgets/column/tests/test_column.py b/src/manywidgets/column/tests/test_column.py
index 2604766..8e205b1 100644
--- a/src/manywidgets/column/tests/test_column.py
+++ b/src/manywidgets/column/tests/test_column.py
@@ -7,6 +7,12 @@ def test_children_positional():
     assert c.children == [a, b]
 
 
+def test_flattens_list_args():
+    a, b, c = Slider(), NumberDisplay(), Slider()
+    col = Column(a, [b, c])  # second arg is itself a list
+    assert col.children == [a, b, c]
+
+
 def test_defaults_and_marker():
     c = Column()
     assert c.gap == "8px" and c.align == "stretch"
diff --git a/src/manywidgets/column/widget.py b/src/manywidgets/column/widget.py
index 81d2267..6fb6ce0 100644
--- a/src/manywidgets/column/widget.py
+++ b/src/manywidgets/column/widget.py
@@ -10,7 +10,7 @@
 import traitlets
 from ipywidgets import Widget, widget_serialization
 
-from .._base import BaseWidget, asset
+from .._base import BaseWidget, _flatten, asset
 
 
 class Column(BaseWidget):
@@ -31,5 +31,5 @@ class Column(BaseWidget):
 
     def __init__(self, *children, **kwargs):
         if children:
-            kwargs.setdefault("children", list(children))
+            kwargs.setdefault("children", _flatten(children))
         super().__init__(**kwargs)
diff --git a/src/manywidgets/grid/tests/test_grid.py b/src/manywidgets/grid/tests/test_grid.py
index 6601277..8a5486b 100644
--- a/src/manywidgets/grid/tests/test_grid.py
+++ b/src/manywidgets/grid/tests/test_grid.py
@@ -8,6 +8,12 @@ def test_children_positional_and_defaults():
     assert g.columns == 2 and g.gap == "8px"
 
 
+def test_flattens_list_args():
+    cards = [Stat(), Stat()]
+    g = Grid(Stat(), cards)  # second arg is itself a list
+    assert len(g.children) == 3
+
+
 def test_columns_kwarg():
     g = Grid(Stat(), Stat(), columns=3)
     assert g.columns == 3
diff --git a/src/manywidgets/grid/widget.py b/src/manywidgets/grid/widget.py
index d774356..1822bcb 100644
--- a/src/manywidgets/grid/widget.py
+++ b/src/manywidgets/grid/widget.py
@@ -10,7 +10,7 @@
 import traitlets
 from ipywidgets import Widget, widget_serialization
 
-from .._base import BaseWidget, asset
+from .._base import BaseWidget, _flatten, asset
 
 
 class Grid(BaseWidget):
@@ -29,5 +29,5 @@ class Grid(BaseWidget):
 
     def __init__(self, *children, **kwargs):
         if children:
-            kwargs.setdefault("children", list(children))
+            kwargs.setdefault("children", _flatten(children))
         super().__init__(**kwargs)
diff --git a/src/manywidgets/lonboard/filter_binder/doc.md b/src/manywidgets/lonboard/filter_binder/doc.md
index f775008..eaf4919 100644
--- a/src/manywidgets/lonboard/filter_binder/doc.md
+++ b/src/manywidgets/lonboard/filter_binder/doc.md
@@ -37,6 +37,12 @@ binder = FilterBinder(slider, layer)   # slider.low/high -> layer.filter_range
 Column(slider, binder, m)
 ```
 
+```{note}
+For **static export**, include the binder somewhere in your displayed layout (e.g.
+`Column(slider, binder, m)`) so its JavaScript activates — an exported page has no
+kernel. In a **live kernel** the binding also works without displaying the binder.
+```
+
 ## API
 
 {api-table}
diff --git a/src/manywidgets/lonboard/filter_binder/src/index.ts b/src/manywidgets/lonboard/filter_binder/src/index.ts
index 2ff519f..0177efb 100644
--- a/src/manywidgets/lonboard/filter_binder/src/index.ts
+++ b/src/manywidgets/lonboard/filter_binder/src/index.ts
@@ -28,12 +28,16 @@ async function render({ model, el }: RenderProps<FilterBinderModel>): Promise<vo
   const label = model.get("label") || `${lowField}/${highField} → ${filterField}`;
   status.textContent = `🔗 filter: connecting…  (${label})`;
 
+  // `layer` may be a single widget-ref or a list of them; resolve all of them.
+  const rawLayer = model.get("layer");
+  const layerRefs: unknown[] = Array.isArray(rawLayer) ? rawLayer : [rawLayer];
+
   let source: ModelHandle;
-  let layer: ModelHandle;
+  let layers: ModelHandle[];
   try {
-    [source, layer] = await Promise.all([
+    [source, layers] = await Promise.all([
       resolveModel(model, idOf(model.get("source"))),
-      resolveModel(model, idOf(model.get("layer"))),
+      Promise.all(layerRefs.map((ref) => resolveModel(model, idOf(ref)))),
     ]);
   } catch (err) {
     status.textContent = `❌ filter: ${(err as Error).message}`;
@@ -44,11 +48,13 @@ async function render({ model, el }: RenderProps<FilterBinderModel>): Promise<vo
   const apply = (): void => {
     const low = asNumber(source.get(lowField));
     const high = asNumber(source.get(highField));
-    const key = `${low}:${high}:${layer.models.length}`;
+    const key = `${low}:${high}:${layers.map((l) => l.models.length).join(",")}`;
     if (key === lastKey) return;
     lastKey = key;
-    layer.setByPath(filterField, [low, high]);
-    layer.save();
+    for (const layer of layers) {
+      layer.setByPath(filterField, [low, high]);
+      layer.save();
+    }
     status.textContent = `✅ ${label}: [${low}, ${high}]`;
   };
 
diff --git a/src/manywidgets/lonboard/filter_binder/tests/filter_binder.test.ts b/src/manywidgets/lonboard/filter_binder/tests/filter_binder.test.ts
index 237f4aa..37e6c50 100644
--- a/src/manywidgets/lonboard/filter_binder/tests/filter_binder.test.ts
+++ b/src/manywidgets/lonboard/filter_binder/tests/filter_binder.test.ts
@@ -45,4 +45,28 @@ describe("FilterBinder", () => {
     expect(p2.get("filter_range")).toEqual([1, 2]);
     cleanup();
   });
+
+  it("writes to every layer when given a list of layers", async () => {
+    const slider = fakeModel({ widget_id: "rs3", low: 5, high: 25 });
+    const layerA = fakeModel({ filter_range: null }, { model_id: "layerA" });
+    const layerB = fakeModel({ filter_range: null }, { model_id: "layerB" });
+    const cleanup = installHostRegistry([slider, layerA, layerB]);
+    const model = fakeModel({
+      source: "IPY_MODEL_rs3",
+      layer: ["IPY_MODEL_layerA", "IPY_MODEL_layerB"],
+      low_field: "low",
+      high_field: "high",
+      filter_field: "filter_range",
+      label: "",
+    });
+
+    await widget.render({ model, el: mountEl() } as never);
+    expect(layerA.get("filter_range")).toEqual([5, 25]);
+    expect(layerB.get("filter_range")).toEqual([5, 25]);
+
+    slider.set("high", 15);
+    expect(layerA.get("filter_range")).toEqual([5, 15]);
+    expect(layerB.get("filter_range")).toEqual([5, 15]);
+    cleanup();
+  });
 });
diff --git a/src/manywidgets/lonboard/filter_binder/tests/test_filter_binder.py b/src/manywidgets/lonboard/filter_binder/tests/test_filter_binder.py
index fa9a54f..d257340 100644
--- a/src/manywidgets/lonboard/filter_binder/tests/test_filter_binder.py
+++ b/src/manywidgets/lonboard/filter_binder/tests/test_filter_binder.py
@@ -1,4 +1,6 @@
 import pytest
+import traitlets
+from ipywidgets import Widget
 
 pytest.importorskip("lonboard")
 
@@ -6,6 +8,12 @@
 from manywidgets.lonboard import FilterBinder  # noqa: E402
 
 
+class _FakeLayer(Widget):
+    """Minimal real Widget standing in for a lonboard layer with filter_range."""
+
+    filter_range = traitlets.Any(allow_none=True).tag(sync=True)
+
+
 def test_source_layer_and_defaults():
     src = RangeSlider()
     layer = Slider()  # stand-in Widget for the layer
@@ -15,6 +23,32 @@ def test_source_layer_and_defaults():
     assert fb.filter_field == "filter_range"
 
 
+def test_accepts_list_of_layers():
+    src = RangeSlider()
+    layers = [Slider(), Slider()]  # stand-in Widgets for layers
+    fb = FilterBinder(src, layers)
+    assert fb.layer == layers
+
+
+def test_python_observer_syncs_without_display():
+    # The binder is never rendered; the Python observer should still drive the layer.
+    src = RangeSlider(low=0, high=10)
+    layer = _FakeLayer()
+    FilterBinder(src, layer)
+    assert layer.filter_range == [0, 10]  # initial sync
+    src.high = 5
+    assert layer.filter_range == [0, 5]
+
+
+def test_python_observer_syncs_multiple_layers():
+    src = RangeSlider(low=1, high=9)
+    layers = [_FakeLayer(), _FakeLayer()]
+    FilterBinder(src, layers)
+    src.low = 3
+    assert layers[0].filter_range == [3, 9]
+    assert layers[1].filter_range == [3, 9]
+
+
 def test_traits_synced():
     for name in ("source", "layer", "low_field", "high_field", "filter_field"):
         assert FilterBinder.class_traits()[name].metadata.get("sync") is True
diff --git a/src/manywidgets/lonboard/filter_binder/widget.py b/src/manywidgets/lonboard/filter_binder/widget.py
index 2027048..09470ba 100644
--- a/src/manywidgets/lonboard/filter_binder/widget.py
+++ b/src/manywidgets/lonboard/filter_binder/widget.py
@@ -4,6 +4,10 @@
 a :class:`~manywidgets.Slider` with ``low_field == high_field == "value"``) and
 writes it to a layer's ``filter_range`` (from ``DataFilterExtension``). Works live
 and in static export.
+
+In a live kernel a Python observer keeps the layer in sync even if this widget is
+never displayed; static export has no kernel, so there the binder must be rendered
+(e.g. inside a ``Column``) for its JavaScript to activate.
 """
 
 from __future__ import annotations
@@ -15,15 +19,24 @@
 
 
 class FilterBinder(BaseWidget):
-    """Bind a (Range)Slider to a lonboard layer's ``filter_range``."""
+    """Bind a (Range)Slider to one or more lonboard layers' ``filter_range``.
+
+    ``layer`` may be a single layer or a list of layers; one slider then drives
+    them all.
+    """
 
     _esm = asset(__file__, "dist", "widget.js")
 
     source = traitlets.Instance(
         Widget, allow_none=True, help="The slider providing low/high values."
     ).tag(sync=True, **widget_serialization)
-    layer = traitlets.Instance(
-        Widget, allow_none=True, help="The lonboard layer to filter."
+    layer = traitlets.Union(
+        [
+            traitlets.Instance(Widget),
+            traitlets.List(traitlets.Instance(Widget)),
+        ],
+        allow_none=True,
+        help="A single lonboard layer, or a list of layers, to filter.",
     ).tag(sync=True, **widget_serialization)
     low_field = traitlets.Unicode("low", help="Source trait for the low bound.").tag(sync=True)
     high_field = traitlets.Unicode("high", help="Source trait for the high bound.").tag(sync=True)
@@ -38,3 +51,22 @@ def __init__(self, source=None, layer=None, **kwargs):
         if layer is not None:
             kwargs.setdefault("layer", layer)
         super().__init__(**kwargs)
+        # Live-kernel fallback: keep ``filter_range`` in sync via a Python observer
+        # so the binding works even when this widget is never displayed. Inert in
+        # static export (no kernel); the JS ``render()`` covers that path. See the
+        # docstring note. (The observer attaches only if ``source`` is set here.)
+        if self.source is not None:
+            names = list(dict.fromkeys([self.low_field, self.high_field]))
+            self.source.observe(self._sync_filter, names=names)
+            self._sync_filter()
+
+    def _sync_filter(self, change=None):
+        """Mirror the source's ``[low, high]`` onto each layer's ``filter_range``."""
+        if self.source is None:
+            return
+        low = getattr(self.source, self.low_field)
+        high = getattr(self.source, self.high_field)
+        layers = self.layer if isinstance(self.layer, list) else [self.layer]
+        for layer in layers:
+            if layer is not None:
+                setattr(layer, self.filter_field, [low, high])
diff --git a/src/manywidgets/row/tests/test_row.py b/src/manywidgets/row/tests/test_row.py
index 6a6d3fc..fb094ac 100644
--- a/src/manywidgets/row/tests/test_row.py
+++ b/src/manywidgets/row/tests/test_row.py
@@ -7,6 +7,12 @@ def test_children_positional():
     assert r.children == [a, b]
 
 
+def test_flattens_list_args():
+    a, b, c = Slider(), Stat(), Slider()
+    r = Row(a, [b, c])  # second arg is itself a list
+    assert r.children == [a, b, c]
+
+
 def test_children_kwarg_and_defaults():
     a = Slider()
     r = Row(children=[a])
diff --git a/src/manywidgets/row/widget.py b/src/manywidgets/row/widget.py
index df6fb28..2aed44b 100644
--- a/src/manywidgets/row/widget.py
+++ b/src/manywidgets/row/widget.py
@@ -12,7 +12,7 @@
 import traitlets
 from ipywidgets import Widget, widget_serialization
 
-from .._base import BaseWidget, asset
+from .._base import BaseWidget, _flatten, asset
 
 
 class Row(BaseWidget):
@@ -34,5 +34,5 @@ class Row(BaseWidget):
 
     def __init__(self, *children, **kwargs):
         if children:
-            kwargs.setdefault("children", list(children))
+            kwargs.setdefault("children", _flatten(children))
         super().__init__(**kwargs)
diff --git a/src/manywidgets/skill/references/widgets-api.md b/src/manywidgets/skill/references/widgets-api.md
index e899fae..9be75b1 100644
--- a/src/manywidgets/skill/references/widgets-api.md
+++ b/src/manywidgets/skill/references/widgets-api.md
@@ -306,7 +306,7 @@ LayerFilter(layer, categories, value, label='Filter')
 
 ### `FilterBinder`
 
-Bind a (Range)Slider to a lonboard layer's ``filter_range``.
+Bind a (Range)Slider to one or more lonboard layers' ``filter_range``.
 
 ```python
 FilterBinder(source, layer, low_field='low', high_field='high', filter_field='filter_range', label='')
@@ -315,7 +315,7 @@ FilterBinder(source, layer, low_field='low', high_field='high', filter_field='fi
 | Trait | Type | Default | Description |
 |---|---|---|---|
 | `source` | Instance | — | The slider providing low/high values. |
-| `layer` | Instance | — | The lonboard layer to filter. |
+| `layer` | Union | — | A single lonboard layer, or a list of layers, to filter. |
 | `low_field` | Unicode | `'low'` | Source trait for the low bound. |
 | `high_field` | Unicode | `'high'` | Source trait for the high bound. |
 | `filter_field` | Unicode | `'filter_range'` | Layer trait to write [low, high] to. |