> ToDos get automatically "done" when you act
Well, that's not flawless. I never use the TODOs view, because it's full of items like this:
https://screenshots.firefox.com/wxy2llOZM5g0HWre/gitlab.com
In other words, there's a number of issues assigned to me listed there, even though they're closed. There's also a few mentions that I don't otherwise interact with (I've seen them in my email and that's that), so I'd have to manually mark those as Done in the GitLab interface after reading them in my email.
The ToDos is a sort of inbox of actionables. We don't use approvers because we use assignees for MRs but here you'll get anything that requires (or may require) some action on your part, like mentions, assignments, CI job failures you're responsible of... ToDos get automatically "done" when you act, such as replying to a mention. Alternatively you can manually mark some issues as "done" or "to do". I like this workflow personally use them to great effect by practicing a form of Inbox Zero, and combined with the personal issues and MR lists they give me a good picture of what I have to do.