Assuming by “on a team” you’re referring to the Associated Team field, then yes, you’re correct that there’s no way other than after the fact (well, there is a way I mention above using our Flowsana integration 
).
This is because Asana has moved away from the concept of a project “being on a team” and toward the concept of a team being a member of a project, which you CAN set when creating a project. The “Associated team” is now legacy concept, might or might not stick around in the future from what I hear. (Note: I’m not endorsing this change, I don’t happen to like it as currently designed; just explaining.)