I tried to bump other threads regarding the loss of this in Grasshopper as well. I used to use the right-click context menus extensively in Grasshopper for Flatten, Graft, Simplify, changing wire display, etc.
It made a really big difference for me to distribute the work between left and right hands - I started to experience carpal tunnel symptoms in my right hand as a result of the increased amount of mouse moves / clicks, whereas before I could quickly hit keys with my left hand.
Using the - key doesn’t collapse all sublayers, it only collapses the immediate layer that you’re selecting. When you expand that layer again, all its sublayers are still expanded in their prior state. I often use collapse sublayers as a way to collapse many nested sublayers quickly.