Cool work :-)
I'd rather have some more control of temporary container names/colours, though: when you open several temporary containers at the same time, having them only called “tmp1”, “tmp2”, etc. may be a little confusing (it's possible to change it in the preferences, but that's not really user-friendly).
I wish the toolbar button could display a small popup allowing to select the name, colour and icon for the container (pre-filled with the automatic settings). Would it be possible?
*EDIT after the answer* I thought it as an option (I presumed that was in the aims of the toolbar popup when activated, but sadly not). I agree that it should not be the default behaviour.