question

You can stop an item on the conveyor . Therefore you must cast the item into an item in the conveyor system. That is why a decision point works with a picklist option and the right reference for the item to stop is set. If you want a conveyor stop items this way, you can set an own created flag and stop all relevant items. Each new entering items are stopped instantly when they enter the system as long as the flag is set to the right state. You collect the reference to all stopped items and resume them when the item leaves the processor.

Flag = a variable, a node, a label, a table cell, or anything that can keep a value that you can set and read by code.