Steps you finish yourself: a personalized email, a reply in thread, or any task.
Open a sequence from "Sequences".
Click "Add step".
"Manual Email" drafts from your template but waits for you to personalize and send.
"Manual Email Reply" does the same in the existing thread.
"Manual Social Step" is a to-do on any channel.
Manual steps show in "Scheduled today" as "Action due". Open the row, finish it, and mark it done.