I assume the total number of items in an order is known beforehand? Then you could track how many items still need to be packed and adjust the Combiner's target quantity accordingly upon receiving the first item.
The On Entry trigger of the Combiner has the "Update Combiner Component List With Labels" option. It contains the code needed to change the target quantity. I would suggest you read through the comments in its code to understand how it works.
In the attached model I altered to look up how many items are still pending in the order (read from global table) and adjust the target quantity down necessary.
If the Combiner is not set to "Join" then the packed items still exist as individual subnodes of the tote. How to handle them further depends on the specifics of what should be done with them. But the overall easiest approach is probably to use a Process Flow.
For example: React to a tote arriving in a queue with an Event-Triggered Source. Create a token for each item it contains (object.subnodes.length). Batch these together and have each batch acquire a processor, then move the items into it. When it finishes, combine the items into one (move all but the first into the first item, or destroy all but one, or ...). Then put them back into the tote.
More details would help to provide a more complete answer. 😉
