pressing the ± keys in the outliner expand and contract things. In the outliner it zooms in and out. Would be nice if they matched so you don’t have to learn multiple shortcuts for the same actions. Would be great if you could press shift + a to bring up an add modifier popup (like in other areas of blender), even more useful in the modifier panel because often the add modifier dropdown is scrolled out of view.
Properties panel doesnt use same shortcut keys for navigation as outliner