WIP but I got my tool manager launching and working in 3dsMax, and redocking of the widgets works too! I was expecting more trouble when having it run under 3dsMax. The blue hover overlay is not however, so I'll have to dig into that a bit more.
And find a way to get Maya so I can get this working in that too. And Blender.
Clip of the tool widget redocking and overlay working in VSCode: