Is it possible to create another branch of the shared tree that I’m not related to? Like creating a branch for a friends family.
From the "Recents" tab dropdown, select "Add Unconnected Person" to start an unrelated branch.
You may find that members of that family/branch are already entered in the tree.
You can work in any part of the tree that you want to. Very often, sorting out one family requires sorting out another family with similar names. It is all good.