Been using this one for over a decade. Works with Firefox’s bookmark keywords feature.
Make a new bookmark, set the link as follows:
https://lemmy.world/c/%s (or your own Lemmy instance)
And in the “Keyword” field, use “c” or “lemmy” or whatever.
Now, when you want to visit a specific Lemmy community on your home instance, you can simply type:
“c community_name” in the address bar, or “lemmy community_name” in Firefox and it will open the community.
It’s using the search keyword feature, where you can right-click on any search field and do this exact thing. Works with most search fields anywhere. I just used it to substitute parts of the URL.