I have added a collapsible view to jostMlib Quark. It has a lot of useful features, like option-clicking to open/close all items in a column.
If anyone is wondering where this barrage of quark libs is coming from: I have decided to use my time, now that I am retired, to abstract the large amount of SC GUI work I did over the last 20 years into some generally usable classes, and to share all that work with the community. I won’t be publishing my entire IDE, because it is MUCH too messy, but I might write a short book about how to create one like on SuperCollider Projects | Jost Muxfeldt . Cheers!