I use i3wm, but what works for me is to use first arandr to setup the screen as I like it. Then I save it to my preferred profile using autorandr. Maybe redundant but easiest for me.
The command autorandr --change
checks if the current configuration corresponds to any of your saved profiles. I implement it in i3 so that when I respawn it loads the command.
So let’s say you save two profile, one only laptop and the other laptop plus external monitor with laptop switch off. Once you connect the monitor your can press your keybindings to respawn/refresh qtile and in principle it should pick it up or you can use the terminal.