References you might consider

[lextm]

• You didn't yet add AvaloniaEdit to this project (but it might be in your backlog), which was derived from AvalonEdit, the core asset of SharpDevelop 4. Though it hasn't been actively maintained for a while, it remains a useful component to speed up the development of a full-featured editor.

• In the same time frame of this repo, another C#-based IDE called SharpIDE has been announced and evolved. You might want to explore there to see if anything can be reused. A side project called SharpDbg is interesting, too. A lot of your backlog items have been done there already.

Ideally, I'd like to see people join forces and integrate their components with others. An IDE is never a small project that a small team could finish or maintain in a reasonable timespan. SharpDevelop/MonoDevelop were popular once, as they were backed by fairly large developers, but even projects at that scale fell into oblivion.

[lextm]

And there is another visual designer by the way. Since the original was part of SharpDevelop 4, many of the designer features (bindings, etc) might have already been there.