I have several one row portals on separate tabs, each showing related records from the same related table. First tab is initial row 1, number of rows 1, second 2 / 1, third 3/1.
I have allow creation... turned on for the relationship. If I have no related records, then in the first tab, the portal is enterable as expected. But , unlike a standard portal, the empty portals in the other tabs show fields and field labels, but they are non-enterable.