Double clicking on a contraption in the patcher pane opens the contraption in the properties pane, if it is not altready open. It would be really cool if double clicking the patcher pane part again (on an open contraption) closed its GUI in the properties pane.
I never thought about that, but it makes total sense.
Yeah, I've been using Mulch for about 15 years, and it only occured to me yesterday! :)