Add to pipeline creates a lead card on New from Contacts, a Unibox thread, or a list selection. The person stays a contact.
Add the card
The contact does not move off Contacts. You get a pipeline card that points at the same person.
On Contacts, open a person and select Add to pipeline, or use Add to pipeline on that row menu.
In Unibox, open the thread and select Add to pipeline on the toolbar.
On a list, select one contact, open the selection menu, and select Add to pipeline. The control needs a single selected person.
Open Leads. The new card is on New.
Source on that card will show Manual or Unibox depending on where you clicked. Drag the card to Qualified, Meeting, Won, or Lost when the deal moves.
What does not change
The person remains a contact you can enroll, export, or message. Adding a card does not send LinkedIn and does not launch a campaign. InMail cannot launch from a campaign either. Use the pipeline for human follow-up, and Campaigns for Message steps.