LO bug forum suggested to raise this bug here:
After setting up a second monitor with ARANDR, LibreOffice Impress shows the presenter console on the primary screen and the presentation on the secondary screen. Pressing the button "Change" on presenter console allows to swap the screen outputs (presenter console to secondary screen, presentation to primary screen). Pressing that button again should swap back, but it doesn't. It is only possible to recover the original settings by disconnecting the VGA cable, reconnecting it and resetting the screen settings with ARANDR.