Hit F10 once, then right-click any window and go to Window Settings. In the Locate area choose On-screen Message. Click Show to show the window. If you don't see it appear, click Center to get it back to the middle of the screen.
Right-click the On-screen Message window and click Window Settings again. The dialog won't look like it changed, but now it's controlling the On-screen Message window instead of the one you first clicked. Now you can change Default Location, Default Opacities, etc. Once you have it like you want it, use the Locate dropdown to Hide it again (you may have to click Show then Hide), then hit F10 twice to get out of that mode.
If it's getting cut off as if it's not resizing, it may have gotten locked inadvertently. While you are changing settings, make sure the Locked checkbox is unchecked.