Filter by floor in multilevels buildings, for 3D mapping

[Martinligabue]

I think a nice feature for the editor would be to add a way to filter by level, so you have less clutter and can easily edit multi-level buildings.

I proposed this feature to iD, but there is an inactive issue here, and a rejected draft of an implementation here.

I imagine it will not be done, as they are usually very busy, but perhaps this feature could be done here in Rapid.