Currently, 3D view active scene and toolstate (i.e. states of the toolbar buttons) logic is distributed between QDS and puppet, with puppet doing most of the work for legacy reasons.

I don't think there is need to have this logic on puppet side these days - QDS should have full control of the active scene and associated toolstate and just tell puppet what to render. The code should be refactored to move the logic for these features entirely to QDS side.

Note that this is quite significant undertaking, so unless there is a major issue related to this, it may not be worth doing.