Wow! That looks good. I think I saw 2 lines of code that I wrote originally.
I think eventually this will be seen as a standard item for FreeCAD, it helps so much in the change from sketching to viewing.
I see what you mean about the docking issue, mine locks up also.
I always use the "Twin aero motor" as my test for a complex model. It is so cool to be able to move around and look inside of it, with almost no effort.
I will spend much time learning what you coded, thanks for that. I like the sliders also and the ability to adjust to 5%.
I have seen a design logic issue (from my version and yours), when going to sketcher the "user" on/off status should change to off. This will show the operator the panel is disabled. It could be re-enabled on exiting sketcher.
I really like the docking, I haven't tried it yet on my dual monitor system, later.
Go to go, it's Saturday, Thanks again. I will test a bunch next week.