Hi Georg,
If you place the mouse cursor over the top border of the Script Editor window, the mouse cursor should change to two vertical arrows, and hence you should be able to click and drag to reduce the window's size. Does this happen?
Anyway you can try this workaround:
- Make sure the Script Editor window is visible.
- Normalize ("unmaximize") PI's main window. If necessary, reduce its size manually.
- Maximize PI's main window again.
- Now the Script Editor window should have smaller dimensions.