I’m afraid I’m still not fully catching up with your own unique case but sounds like there is always a variable involved in your copy operation to determine where rows are finally associated.
What about firing one action first ? This action will create new form with column value in parent row where we pass the values of request fields from the selected parent? The hide those fields in the form and let the user to select out of Dropdown to decide where the destination is. Then save this form. Then upon saving the form it will fire the rest of actions , copy parent along with child’s. At this point of time we know destination. In your working case it looked like to me the user need to select the destination after copies are made. But my case, selection of destination is part of chain of actions.