I track my actively played games in the Playthroughs tabs. For a small amount of games, I can import existing goals. For others, I need to create them manually.
Can other players import goals created by me for the same game, or can they only be imported from some specific people who are allowed to share them?
The only game with an import option was the one I started from the bounties tab, all other games I have there have the import option locked. What decides which games can have the goals imported and from whom?

The goal templates that are available publicly are added by curators/admins to the database since templates are a WIP feature. They aren't imported from our personal playthrough goal lists, but rather created explicitly as a public template.

Any goals you create for personal use aren't added to the list of publicly available templates.

If you click "Browse Database -> Goal Templates" you should be able to see & search the games with this feature