Priority rows
A priority row sends first. A contact who matches its filters gets that row's messages before any alert, scheduled row or rotation, once through, and then carries on with the rest of the campaign. Use it for a welcome.
Making a row priority
On the campaign's Setup tab, click the schedule text on a nurture row, tick Priority: send this row first and save. The row then reads Priority in the list.
A priority row is always limited. A recurring row would never finish, so it cannot be priority: ticking Priority makes the row limited, and an API call that asks for priority on a recurring row is refused.
Alert and scheduled rows already go before the rotation, so only a nurture row can be priority.
Several priority rows
They go in row order. A contact gets the first priority row they match and have not finished; when it is done, the next one they match; then the normal campaign.
The rotation does not move
A priority send is not a turn of the rotation. A contact who was due the case study pool before the welcome is still due it after.
Timing
A priority row goes first the next time the campaign is called. The campaign has no timing of its own; the flow or the HubSpot workflow decides when that is. See Timing: where it lives.
Checking it
Run a dispatch preview for a test contact. The priority row reads matched; priority when it is the one that goes.