Sorry, I could have been a bit clearer. It’s a command you have to run in macOS Terminal. It looks a bit intimidating, but actually it’s quite easy to do:
- Press Cmd+Space to open Spotlight.
- Type “Terminal” without quotes and press enter.
- You should see a command prompt waiting for input in the Terminal app.
- Copy the following command (the complete line) with Cmd+C and paste it into the Terminal window with Cmd+V:
/System/Library/Frameworks/CoreServices.framework/Frameworks/LaunchServices.framework/Support/lsregister -kill -r -domain local -domain system -domain user
- Press Enter and wait a few seconds until it is finished.
- Restart Safari and check the Extensions page in Preferences, the Bitwarden extension should be back.
The command simply resets a list of so-called Launch Services that macOS retains and registers these services again. Why this is necessary is beyond my abilities, but it helps and causes no other problems.