In dark mode in the Windows app, the location indicator/cursor for collaborators is not visible (the thin vertical line). Only if you happen to mouse over the invisible cursor will you see that a collaborator is there.
Also, I don’t know if this is related, but the profile pictures of collaborators at the top of the entity view are not always present. They are sometimes there, and sometimes not. When the picture above was taken, there were not any collaborator pictures at the top of the view.