If you manage a lot of pipelines you will be pleased to hear that we've added the ability to archive pipelines that are no longer in use. Archived pipelines have all their historical data preserved, but won't run new builds, and are not shown on the Pipelines page by default. You'll find a list of archived pipelines in the Team Selector:

Archive pipelines from the Settings page, under Pipeline Management, or using the GraphQL API.

Happy Archiving!