Hi Nikolay & al.,
I'll include a new command in version 1.6.1 to reset the geometries of all process windows. For now, you can perform a full reset to restore everything to default settings. There is an option in Windows to do this: Start > All Programs > PixInsight Platform > Reset PixInsight Settings. Alternatively, you can launch PixInsight with the Ctrl key pressed. This works on all platforms.