If you see this message when attempting to delete a pipeline, it means that the pipeline cannot be deleted because it has projects connected to it. This applies regardless of the project's state (e.g., open, won, or any other status).
To delete a pipeline with connected projects, follow these steps:
Navigate to Projects in the left menu
Choose list
Filter on the specific pipeline
Click on the three dots
Choose to remove or edit the project. If you choose edit you can easily change the pipeline if you scroll down the project card
When you have moved the connected projects you can go back to the administration view and choose to delete the pipe.
Congratulations! You have successfully deleted a pipeline with connected projects.