Is there a console command to add specific god challenges?

Don't think so.

Yes, I successfully used the command

SetGodChallengeEnabled <challenge> <value>

where <challenge> is one of {berath, magran, woedica, etc.}

and where <value> is one of {0, 1}.

0 = inactive

1 = active

 

For example, the command

SetGodChallengeEnabled woedica 1

should enable Woedica's challenge in a current playthrough.

Edited May 22, 20196 yr by Mallard

Interesting! What about Vela? Does she suddenly appear after the command for Hylea's challenge gets executed?