When I’m using the Citrix virtual desktop software (sadly big in business and healthcare) in UB 18.04 moving the mouse pointer to the top and sides does not trigger the panel or Plank. Interestingly, the hot corners app still works, as does alt+tab. If the Citrix window is active and full screen then detection is fine, it’s only when the window is full screen.
I was wondering if this is a Citrix thing, but this same functionality is fine on my UB 17.10 install (although I’m using dual monitors there, so it’s not exactly the same). I can test it on the dual monitor later to see if it’s an 18.04 thing. I can also post a video if needed later as well.