Asked the dev about this, and got a reply that I thought somebody else might find useful.
ForkLift supports URL schemes of the format:
forkliftfav://F1061903-DA63-4D3C-A839-A2DD72438471
where everything following the :// is the UUID of the “Favorites” item in ForkLift. The UUID isn’t exposed in the interface, but it’s in the file:
~/Library/Application Support/ForkLift/Favorites/Favorites.json
Easy enough to find if you really want it. Personally, I’m dropping ForkLift URLs into associated project folders so I can get to it easily from Finder for web projects.