firejail firefox help

[Adam Funk]

I have a Firefox browser profile called "open", which has a few
add-ons and basic bookmarks, but no restrictions on scripting, so I
prefer to run it in firejail.  At the moment I'm using this command to
launch it:

firejail --private.keep=.mozilla/firefox/profiles.ini,.mozilla/firefox/b7jxnp0d.open firefox -no-remote -P open

Obviously when I want to make changes (e.g., changing the Ublock
filters), I have to run Firefox with that profile outside of firejail,
make the changes, & quit to save them.  Then the next run in firejail
picks them up from the profile directory.

This is great except for one problem: it's impossible to download
anything deliberately, because the "Downloads" target directory is
inaccessible outside the firejail.  Is there a way to add one writable
persistent directory to this?  (I tried combining
--private.keep=.mozilla.stuff and --private=Downloads, but that gave
an error message.)

Thanks,
Adam