How to Fix Windows Appearing Off Screen on Ubuntu Dual Monitor Setup

Probably applies to other Linux setups also ...

https://linuxvox.com/blog/window-appears-off-screen-on-ubuntu/

"If a window is partially visible (or you can select it), use keyboard shortcuts to drag it back into view:
    Grab the window:
        Click the window to focus it (or use Alt+Tab to select it).
        Press Alt+F7 (hold Alt, then press F7). The cursor will turn into a "move" icon.

    Move the window:
        Use the arrow keys (↑ ↓ ← →) to drag the window into the visible area.
        Release the keys when the window is centered on a monitor.

If a window is entirely off-screen (no title bar/edge visible):
    Select the window: Press Alt+Tab repeatedly until the window is highlighted (you’ll see its preview).
    Grab and move: Press Alt+F7 to activate "move mode," then use arrow keys to drag it into view.

Lots of other options in the article.