@Peter.Chaushev can you reproduce this in Rhino?
Run the command “NewFloatingViewport” to create a new floating perspective. This new window disappears for me whenever I open the V-Ray Asset Editor. Plugin version is v4.10.02 Nov 6 2019.
I have to click back somewhere in the other Rhino Viewports for the floating one to reappear.
It’s a bit problematic especially when setting up the camera resolution, and wanting to double-check with safe-frame.
If not the same, it seems vaguely related to: