I had to do this (OAK-DEN-LGA) a few months ago in order to get the connection! I believe there was at least 45 minutes of connect time, maybe more, but no way to do it on the site. And I did it with points but that doesn't matter. Caused a bit of confusion at the airport when checking my bag since she redid everything making my low A connection boarding pass a C but someone was able to reverse it...