question

You need an attribute on the flow items, which contains the information where the flow item is created. Typically you put such a information into a label. Every flow item gets OnCreation in the source a label with the same name but a different value where its heritage is.

You put a Decision Point (DP) on the conveyors, which are involved in the diversion. One on the conveyor (1) on which the flowitems are together and on each where the flow items should travel separated from another (2) and (3). You connects the DP1 with an Object Connection of the Type A with the DP2 and with DP3. In the DP1 Properties you use the Arrival Trigger picklist option Send Item By Case. Then you run the model and stops it, when you see an item from one of the sources you want to separate on the conveyor. In the on trigger function send item by case you find in the line Case Function on the right side an eye dropper tool. You fetch this tool to select with the tool the visible item. You find a list containing severel entries. One points to the label on the item. You select this. In the parameter window of the trigger function you press twice the green plus sign to add cases. You have only to exchange the values to match with the value on the label on the item at each case. Here you see it would be helpful to assign number data to the label at the items to make a separation easy.

Reset and let run the model. That's it.