When running email Cadences, you can select Prospects with different email engagements (for whom the Cadence has been completed) and add them to another Cadence. 

Select any Cadence and click on the Prospects tab. Click on the filter and select any Engagement. This will give you a list of all Prospects who match that filter.

Add these prospects to a new list. You can either choose an existing list or create a new list as per your requirement.

Go to the Prospects page and select this list to add to a particular Cadence.

For future prospects, you can automate this process via Playbooks.
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