The display configuration applet uses "Switch to external screen" and "Switch to Laptop screen" in the tooltips describing some of the actions, which makes little sense when running a multi-monitor setup on a regular desktop. It should either use generic nomenclature like "Switch to Primary/Secondary screen", use the monitor names like "Switch to AcerXYZ/ViewSonicXYZ" or detect the type of system and only use laptop/external when actually running on a laptop (hostnamectl can do this).
*** This bug has been marked as a duplicate of bug 445553 ***