For instance, in the settings page for Tab Session Manager, you can click an upload button to upload JSON session files from your device to the addon. I looked up if UBlock Origin Lite (the re-implementation of UBlock Origin with Manifest v3) supports custom filter lists and all the results said no it can’t due to the limitations of Manifest V3. OTOH I found a StackOverflow post and Google Groups discussion saying its possible with the filesystem API.
Firefox isn’t forcing Manifest V3, is it?
They are forcing MV3. They wrote a blog post about it a while back. But there keeping some of MV2
Edit: found the post. https://blog.mozilla.org/addons/2022/05/18/manifest-v3-in-firefox-recap-next-steps/
From an update from last week:
Oh that’s fantastic! Thanks for the update.