I wish I could filter/sort by whether a module is in the rack I am currently viewing. This would mostly be useful with the "My Modules" tab while editing a rack. When I am rethinking a rack layout, I'd like to quickly pull up my modules that are currently not in the rack, so I can see what I might want to swap in and out.

Not sure how generally useful this feature would be, but as someone with more modules than HP and a frequent rack rearranger, I would use this feature pretty often.