I recently started pyside6-designer from the command line and not from Qt Creator and thought it got broken.

• I used commercial 6.6.1 wheels from qtpip on macOS 14.2 
• I started pyside6-designer w/o argumenta from a terminal running as an app on the secondary monitor, but  pyside6-designer  appeared on the primary monitor. This is a different behaviour than other Qt-based apps the same macOS on the same machine. They always appear on the same monitor from which they were started, basically the same ways as all other apps
• Only one window was visible, see "Screenshot 2023-12-18 at 16.24.49.png"
• A change of focus to make a screenshot, revealed other windows out of a sudden, see "Screenshot 2023-12-18 at 16.25.15.png"
• Another change of the focus made all windows (incl. the first one) completely disappear, only a click on "Show All Windows" made them visible again
• In the later use, it tuned out that all top-level windows of pyside6-designer become hidden each time, the focus switches to another app. In order to make pyside6-designer visible again, it is needed to click on its icon in the launcher bar