I don't know how the syncing works for that, but all my custom bangs (which for me includes bangs for Kagi lenses / filters and non search engine sites at this

I don't know how the syncing works for that, but all my custom bangs (which for me includes bangs for Kagi lenses / filters and non search engine sites at this point) sync using my Kagi account which is pretty nice. Also I use Firefox Focus on mobile, which doesn't have many settings, and I don't think I've seen that features there.