Similar to Tabbed Project browser idea, Type properties should reside within several tabs in the properties panel. This to avoid editing nested properties multiple windows deep (e.g. when editing Floors, Walls, Curtain walls/systems Roofs, Railings or Stairs), nested properties should be in tabs within the Properties panel. Advantages: reduced mouse clicks, no more windows on top of windows and an unobscured viewport to actually see the changes made to the family! The buttons should change depending on the selected family category to be as convenient as possible.
A few examples:
Curtain walls should have tabs for mullions (to edit any mullion types associated to the curtain wall)
For wall properties:
For type properties:
The mullion tab should show all mullions assigned to the curtain wall so you can immediately edit the mullion properties in the properties panel (no more of: find the mullion type in the browser, edit it's properties, select the curtain wall, edit type and reassign mullions).
For walls, there would be a tab for section edits wall structures (edit assembly) and for sweeps/ reveals.
For stairs, this would be especially neat, as you would have run types, left support type, right support type and middle support type all available in one click. Stairs editing in Revit will be simplified as you won't have to go through so many windows.
Essentially all type properties are converted to single tab acces in the properties panel, regardless of the family category.
This idea is a rephrasal of an older idea:
[UI/UX] Flat UI instead of many pop-up windows