question

In your process flow, before you load the rack, you can assign the queue it is located in to a label on the token with

token.rack.up

"token.rack" references the flowitem and ".up" returns the object the flowitem is currently in. Then you can just use another travel/unload activity to transport it back there from the picking station.

210724-kiva_1.fsm

Some other tips concerning you model:

- You should avoid mixing 3d-logic (use transport, port-connections,...) with process flow logic as this might create conflicts how/where an item should be moved.
(For example once the racks re-enter the queue they will be pushed to the list twice, once by the "Send to Port" of the queue and once in the process flow. At that point, two robots might try to move it at the same time.)

- In your process flow you use both an "Unload" and a "Move Object". You only need one. In fact, using both can again lead to problems, as some events might fire twice. The difference between those activies is that "Unload" uses a task executer and prompts it to move to the destination before unloading. "Move Object" essentially teleports the item and worls instantaneously.