Windows sometime doesn't select NVIDIA gpu as preferred graphic processor for gmsh
While I never had an issue using gmsh on Ubuntu 20.04, when opening some complex models in Windows instead, it would get extremely slow at panning/zooming/moving around. I realized I needed to force the selection of the graphic processor in the NVIDIA control panel.
This is just a note for people who might have experienced similar issues as it is not exactly a bug. However, I didn't find any F.A.Q. or similar topic discussion.
If you right-click in the desktop, select NVIDIA Control Panel and in the "Manage 3D settings" and "Program Settings" you can force gmsh to run using the dedicated graphic card instead of the integrated one.