Option to delete your chat history granularly

It is already possible to delete all your messages in user settings, is that what you are looking for?

That's one of the options, yes. I'd prefer if I could get a more granular control though. Per community/channel, for example. Perhaps even an option to delete your entire presence in a server if you leave it, or some such? EDIT: Updated the OP to reflect the "Delete all my messages" button, as I had missed it.