[Feature Request] Inbox Pins

For the most part, I like the inbox. It helps me to see what messages need my attention without losing the notification for the ones I can respond to later. Unfortunately, I am not able to find those messages when I want to, and that makes this task difficult. I propose a "pinned" tab in the inbox, similar to the "this server only" tab. I would like to be able to manually pin messages to my inbox such that only they show up on that tab. Additionally, I propose that pinned tabs should not expire after a week like other inboxed messages do. Not only would this increase the usefullness of yhe inbox feature, it would also keep the inbox organized.