If I close GIMP with the x on its window, everything works fine.
But most of the time I have so many images open that I do not want to close each individually. In this case, I go to the Ubuntu sidebar, right-click on the GIMP icon and click quit
If I do this, all images are closed, but unfortunately when I start GIMP again, the layer and toolbox window are closed and I have to reopen them (Windows->Recently Closed Docks -> Layers and Windows->Recently Closed Docks -> Toolbox).
Is it possible to tell GIMP not to close the layer and toolbox window each time I quit it?