Does that addon require 1password’s desktop program for this feature?

In that case you’ll need a little additional setup, but hopefully not much.
The feature addons use to communicate with a program running outside of the browser is called Native Messaging. Basically it’s happening through a (text?) file. The desktop program probably looks for it in the firefox user data directory instead of the librewolf user data dir.

For now that’s enough, if it turns out that this is the case I’ll fill you in on how to make it work.