Unfortunately you can’t see the total size of the trashbin in the webui. You can cd into data/user and use du -hsc files_trashbin to see the size of the trashbin like you already said. To completely clear the trashbin of a user, you can use occ trashbin:cleanup username. you can also use this command without a user to clear all trashbins. If you only want to delete files that have a certain age, you can use occ trashbin:expire username in the same fashion. this command uses the trashbin_retention_obligation in your config.php, which by default should be set to 30 days. You can change the lifetime of files by changing this value, i will link you the right documentation so you can see how to set it to a specific value.