Howdy Supertux and welcome to the forums!

normally what i do is drag my alts up to the quest giver, making sure the QG is on one side and the camera zoomed all the way out... then i toggle on the mouse-click-passing (MCP).... then click the giver... watch the clicks go to the other screens.. click again if needed... then toggle it off.

to set the hotkey for mouse-click-passing (MCP) , go to keyclone/setup/general... click in the hotkey spot (to the right) of the MCP field.. and hit your key (hitting DEL will clear the hotkey)

let me know if that works for you.