Global option to always launch with 3d view minimized. 3D rendering adds considerably to startup time, esp. on resource constrained hardware. Today view state seems to depend on the file opened and the last view state when saving the file. This make it unpredictable how long one has to wait. Option would also help reducing energy footprint.
Global option to initially keep _at most_ X niveaus visible or use default visibility setting. Having an upper limit also helps with startup time on resource constrained hardware or for large models.
Niveau context menu to (enable|disable) visibility of niveaus (left of|right of) the current niveau tab. Helps to disable multiple niveaus all at once. Esp. helpful for larger house models with multiple niveaus. Similar to "Close all tabs left|right of the current tab" in modern browsers but makes much more sense in SH3D ;-)
Move option "Aerial view centered on selection" into 3D View context menu or into "Modify 3D view..".
Thank you very much for providing us with SH3D. Would be happy to contribute the ideas myself if this was a project on GitHub.