You can add parents or children to an arbitrary org unit (including course offerings) with one of:
- http://docs.valence.desire2learn.com/res/orgunit.html#post--d2l-api-lp-(version)-orgstructure-(orgUnitId)-children-
- http://docs.valence.desire2learn.com/res/orgunit.html#post--d2l-api-lp-(version)-orgstructure-(orgUnitId)-parents-
You still need to create the other org unit or have it created already before calling one of these.