I found
this article about HTC GDR2 update. It says to recover temporary file space out of Other Storage, you have to download the Make More Space app from HTC, which has options to reduce music+videos, pictures, documents, apps and temporary files. When I click on temporary files, it registers the selection (you can see the text shift a bit) and then it does nothing. Selecting any of the other options takes you to the appropriate app/hub to allow you to erase media or unload apps. So I would call Make More Space a bust at this point.
But hey, FM radio.