You can do this in Duet (http://duetapp.com http://duetapp.com), but it's self-hosted. Pretty sure Flow also lets you switch back and forth between boards/lists

You can do this in Duet (http://duetapp.com http://duetapp.com), but it's self-hosted. Pretty sure Flow also lets you switch back and forth between boards/lists. Have to imagine a bunch of other apps have it too.