Would LOVE ClickUp Integration, so that we can create tasks easily within the Missive client etc. I have also requested this of ClickUp but figured it's a good idea to mention it here, too!
integrate the calendly sidebar view (from their extension) into the built in sidebar
Integration with Notion
www.notion.so is a really cool to-do list / evernote & airtable competitor. It would be rad if it was supported as an integration with Missive!
Trello Integration - Link to existing cards BY BOARD
The new Trello integration is 🔥 But... we have dozens of boards, often times with similarly-named cards, so the "link to existing card" functionality is kind of uselsess as-is. Too difficult to figure out what the right card is or guess what we may have called it. It'd be great to be able to filter your search by board, or even better choose a board and see a quick list of cards in that board that we can just click on to select.