Drop the action Abonnement / désabonnement à une liste into your workflow and pick the target list. The contact currently flowing through the automation joins (or leaves) that list. It is free, synchronous, and especially useful for moving contacts from a "raw" list to a qualified one after they meet some criterion.
The most common pattern: promote between lists
You collect leads into a "raw" list, run a welcome workflow that emails them, and at the end of the workflow you add them to "qualified-subscribers". The opposite works too: trigger on inactivity, remove the contact from your main list. The action runs synchronously, so the membership change is visible before the next step.
It also triggers the next workflow
An AddList action will fire the EventList trigger of any other workflow that is watching that list — same as if the contact had subscribed through a form. This is how you chain a welcome flow into a long-running nurture flow: AddList nurture-track at the end of welcome, EventList trigger on nurture-track kicks off the second workflow.
Removing from a list
The same action handles the opposite direction. Use it to clean up: after a renewal, RemoveList renewal-needed so that workflow stops watching. Combine with OncePerDay safety and you have predictable list hygiene without manual work.
Promote and prune lists automatically
Browse the automation actions and pair them with the right trigger.