AME Question . How to Find User id from session

We are configuring GL Approval rule in AME. We have a situation where first user enters journal and check fund/reserves it and then the second user in GL submits for approval. The journal should route to approval to second person's supervisor and not first person's supervisor.

The GL Approval seeded attribute uses user_id from created_by user, which doesn't work for us.

Is there a way we can read the user_id from session of the person logged on and submitting the transaction. Is there any such attribute or can we write one. I am not sure if we can use user_id from session in AME queries.