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If you have an existing Subscriber already in the midst of your Welcome Sequence, and then they opt in for your ConvertKit Cheatsheet Sequence, you might want to pause the Welcome Sequence until they've completed the Cheatsheet Sequence.
Using an Automation Rule
Create an Automation that adds a Tag when a user is subscribed to the Cheatsheet Sequence. We'll call it the "Cheatsheet Sequence."
Next, create a second Automation that removes the Tag when a user completes "Cheatsheet Sequence."
Exclude the Tag "Cheatsheet Sequence" from your Welcome Sequence.
This set-up allows you to exclude only the Subscribers that in-progress. If you excluded the entire Cheatsheet Sequence itself, they would never return to the Welcome Sequence, because a Sequence is not removed from their Subscriber profile.