After issuing a command like xrandr –output LVDS1 –off, you can switch to a console (--), edit /home/user/.kde/share/apps/kscreen/filename (where filename is the one from that directory that was last modified) and change “enabled” : false to “enabled” : true.

[ { "enabled" : false, "id" : "LVDS1", "metadata" : { "name" : "LVDS1" }, "mode" : { "refresh" : 60, "size" : { "height" : 768, "width" : 1366 } }, "pos" : { "x" : 1280, "y" : 128 }, "primary" : false, "rotation" : 1 }, { "enabled" : false, "id" : "thisid", "metadata" : { "fullname" : "thisname", "name" : "VGA1" }, "mode" : { "refresh" : 60, "size" : { "height" : 1024, "width" : 1280 } }, "pos" : { "x" : 0, "y" : 0 }, "primary" : true, "rotation" : 1 } ]