If you can't publish the workflow named "05a - unique nurture" due to the error above saying, "Add to Workflow - Send Purchase Link is missing required attributes: workflow_id. Please add the required attributes and try again.", that is because you need to add the workflow named "03-send purchase link" to the workflow action named "Add to Workflow - Send Purchase Link". This is still within the 05a - unique nurture workflow.
When editing the 05a - unique nurture workflow, simply go to the bottom part where you can see the action, "Add to Workflow - Send Purchase Link"
Edit it, and in the Workflow dropdown, search for "send purchase link." You should see the workflow "03-send purchase link" there. Go ahead and select it, then save the action, then save and publish the workflow.
