This is the most awkward bug (or feature, in case they’ve lost their minds) that I’ve run across in 3.5 so far. I was looking forward to finally use ref planes in ZB, but this makes them practically useless. Placing the ref in front works to some extent, but if you do that you can only see the selected sub tool through it, while everything else is invisible. You can’t control opacity of the plane either.
The model opacity slider in the old image plane plugin seems to work though, so you can still place the refs on canvas as before.
[edit]Turns out that’s not such a good idea. Move tool in 3.5 seems to behave even more erratically than in 3.1 when there is a filled canvas pixol behind the cursor. Wish they’d get that fixed already, it has been real pain in the tail since v2 at least.