[Izkata]

> This already "exists", go to a label, tick the top checkbox above all the rows, then "Select all 5,192 conversations in 'ThisLabel'", then "Delete".

Also works with any search.

> "Exists" in scare quotes because their own interface is absolutely atrocious for doing this, as on e.g. a label with ~50k messages (I was mass-deleting some large mailing lists recently) there's maybe a 5-10% change the operation will eventually finish, and not just leave it at ~45k or whatever.

I've found it to work fairly reliably with that much or more, if you leave the tab open and just wait. It seems to do an initial UI update with those ~5k or so, then continue deleting in the background. Feels like it's done entirely in the frontend, where it deletes a batch, grabs the next, delete, grab next, delete, etc etc etc.