I'm adding a bunch of people manually.
Sometimes when I add a new person, the resulting profile page has a link that says: "Father?"... "Mother?" enabling me to add a parent directly from the Profile page.
Other times there are no such links and to add a parent, you first have to go to the Edit tab, and add from there.
I was trying to find a pattern-- maybe it was a 200-year thing. But as far as I can tell, there is no rhyme or reason behind it being one way or another.