Disable Speculative Connect and Download
As a follow up to #25770 (moved), it turns out Tor Browser actually begins (and sometimes completes) the download before the user can confirm they actually want the-thing. This manifests in #7449 (moved) and #11254 (moved) as the file being downloaded in /tmp (on Unix, or similar on other platforms) and then it is moved into the correct directory.
This provides an obvious performance improvement, especially for our use case. Unfortunately, this download begins before the user is even given the "where do you want this file saved" prompt, and I'm worried subtly downloading a file in the background is dangerous is some context, particularly some of our users.
To upload designs, you'll need to enable LFS and have admin enable hashed storage. More information