I've always wished that Gmail (or some other email client) would add support for creating arbitrary "folders" each with an "inbox" and an "archive" section.

The Gmail inbox -> archive flow works really well, but I'd like to have multiple such inboxes for different mailing lists.

A prime example is pull request notification emails: I want them to skip my inbox and go into a "folder", but I want to keep track of which ones I still need to review so the archiving model would be great.

I could hack such a workflow together using multiple labels, but it wouldn't have the convenience of a universal "archive" keyboard shortcut / button.