I used the Updates feature & later noticed an Update folder in my tce/optional folder. This has now vanished. How / when did this happen?
To help with the full explanation - the updates feature checks your current extension versions against the repo and lists those that have a newer version in the repo.
To guard against the possibility that some of the extensions to be updated are loaded, the update function creates a folder /tce/update and downloads the updated extensions to this folder.
The next time you reboot, any extensions in /tce/update are copied to /tce prior to loading any extensions listed as "onboot" or "ondemand" and once completed, /tce/update is removed.