Firefox extensions are not downloable via right-click in Tor Browser
https://blog.torproject.org/blog/tor-browser-553-released#comment-162846 reports that Firefox extensions are not downloadable with a right-click in Tor Browser:
When I go to https://addons.mozilla.org/en-US/firefox/ pick any Addon extension, right-click on the + Add to Firefox button, and select Save Link As... it fails, TBB downloads a 0 Byte empty file onto the hard drive.
This happens on Linux as well.
To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information