Use the Call instruction with the pxStartRunById activity to start an external data flow run that has already been created. You need to provide the run ID.
Create an instance of the Activity rule by selecting Activity from the Technical category.
In the activity steps, use the Call pxStartRunById method:
Add the first step:
Method: Page-New
Step page: runOptions
Add the second step:
Method: Call pxStartRunById
Step page: runOptions
In the second step, click the arrow to the left of the Method and specify the runID parameter.
Click Save.