Created attachment 169873 [details]
main canvas window and filter mask window after moving the filter mask window

SUMMARY
The apply a filter mask window hides the main canvas.

STEPS TO REPRODUCE
1. Open a project with a picture within a layer
2. On this layer, add a filter mask.
3. Stay in the filter mask configuration window on top of the canvas.
4. Now try to move the filter mask window to the side. The goal is to be able to see the canvas and the live preview of changes you would apply with the filter mask on the canvas.

OBSERVED RESULT
As soon as I move the filter mask window, the main canvas window shrinks in size and moves along with the filter mask window. The canvas window is continously placed behind the filter mask window and hidden. 

EXPECTED RESULT
As tested on Windows 10, I would expect the filter mask window to be movable independently from the main canvas window. I would expect that the main canvas window in the background keeps its size and position on the screen.
This is needed to be able to see the preview of the applied changes of the filter mask directly on the canvas.
(On Windows 10, it was working)

SOFTWARE/OS VERSIONS
Windows: Windows 10
Linux: Zorin OS 17.1

ADDITIONAL INFORMATION