Help with modifying one of Shopify's email automation workflows

Shopify Email App

I want to change the Welcome email series (discount with reminder) automations and add in from their Welcome automation excluding customers who subscribed at checkout. I know how to that BUT in an ideal world the link from that new check would go back into one of the existing workflow boxes. At the moment I can only duplicate the workflow I can’t find a way to connect two parts of the flow to one existing next step so I don’t have to duplicate? Any ideas?