AWS state machine wait on another state machine

Question

I have a state machine (say A) that should wait on another state machine (say B). Now the problem is there could be multiple executions of state machine B and A should execute on a schedule if and only if there are no executions of state machine B running at the same time. It will be complicated to code parallel state and start state machine A as there could be up to 50 executions of state machine B.

Trying to see if there’s a native way to make this work without lambda and dynamo db.