Can't open Quick Settings after connecting external display

I can still interact with the pinned ones, but QS won’t extend to reveal the brightness slider, etcetera. After disconnecting the external display, the problem remains

It’s currently T01:51:36+01:00, so I’ll evaluate whether

  • [ ] it persists after a reboot
  • [ ] it recurs after reconnection of the external monitor

I’m posting this anyway rather than keeping it as a draft because I have some more to post, and so that those who have experienced it that might happen to see it might affirm this experience.