When you hide bones and slots, the attachments should show up in an "Attachments" node in the tree. It's wrong that you see only "Draw Order" (which is for showing slots).
If you restart Spine it should update to 3.2.01 and fix the problem you are seeing. Also the tree filter changed slightly: the individual bones, slots, attachments buttons are back (in addition to the filter button). Here is what it looks like in 3.2.01:
Loading Image
