Curious LXQT problem: adjust window size

Hello, I have a BBB with a 4D Systems LCD cape screen. Resolution: 480272. On one system my gui application runs fine. On another the size of my window is bigger than the display. Must be some parameter in LXQT as the application is identical. In my Python application I have: root.geometry("480272"). But this does not make much of a difference. I tried to find the right LXQT option menu, but that seems inaccessible as most menus are bigger than the screen and it is impossible to “raise” the window. Is there a Debian command available or do I have another option?
Thanks in advance,