Improve "Label" system (stop having menu close automatically, allow filtering by multiple labels at once)

[moikchap]

It seems that I can't create multiple labels in a row (I'm using Opera). The label menu closes automatically after I create one, and when I re-open the menu, the label isn't showing. I need to refresh the page to use newly created labels. 

Possibly related, I can only toggle one label at a time. The menu automatically closes after I make a change, so I need to keep re-opening it until I'm done.

As well, the dropdown for filtering the conversation list via labels only allows using one at a time. Personally, I would prefer at least two since I'm labelling both by gig category and delivery value. Under the current system I need to go back and make more labels which combine the distinctions, and it's a nuisance given how the menu keeps closing after each action.