Add "Valve" to manifold schema and make them available for cloning,

[Torkeug]

Is your feature request related to a problem? Please describe.
Trying to use the "Extend" feature, but if there's a valve involved, the pipes are not copied.

Describe the solution you'd like
Add "Valve" to manifold schema and make them available for cloning,

Describe alternatives you've considered
It would be fine with me if valves are replaced by pipes and I have to put them back manually.