From the bug report , which also has a screen shot mock up "This would make it easier to identify the folders of diffrent mail accounts. This would also make sense for the top account nodes."
Regardless, you might want to vote for https://connect.mozilla.org/t5/ideas/please-allow-for-quot-fixed-quot-locations-for-delete-and-other/idi-p/66248
Does Bug 844475 - When selecting multiple messages, archive and delete buttons should use the same position and visibility as when selecting a single message - describe the issue?
