If you want to switch an existing sequence to conditional, the easiest way is to duplicate the sequence, add your conditions, and then move any contacts in Throttled status to the new sequence.
Since you can’t make changes to steps once contacts have already completed them, duplicating the original sequence gives you the flexibility to smoothly add condition steps and continue.
This article walks you through the process step by step.
1. On the Sequences page, click the three dots next to the sequence and select Duplicate.
2. Add the condition steps to the duplicated sequence.
3. In the People tab of the original sequence, apply the "Current step is Throttled" smart filter to find contacts who haven't progressed.
4. Move these contacts to the new sequence, and you're all set!