When experimenting with building projects, it's likely that some active projects are no longer required despite having time, expense and invoice entries. Unwanted projects can be marked as Test and then deleted.
In your active project, click the More button and select Edit:
The Edit project dialog box appears:
When you scroll to the bottom of the dialog box, you will see the Test project section. Select Yes, to turn your project into a Test project. Then, click Save.
Back in the project, click the More button and you'll see a Delete option:
The confirm dialog box appears:
Click Proceed to permanently remove the project.
If this project was connected to a deal in HubSpot, or an opportunity in Salesforce or Dynamics 365, the link to the project will no longer appear in the deal or opportunity however any activity feed coming from the project will remain in the activity feed of the deal/opportunity.