Move sub-category to different category
I use tasks to track work to be done to take a Prospective Client to becoming a Client and then for managing work when they are a client. But Prospect/ABC cannot be changed to Client/ABC and I have to create a new sub-category and then delete the old one losing data in the process.
You don't have to delete a project to move it under a different project. You can hover over a project and us the handle that will appear on its left side to drag & drop it to move it under a different project.
Alternatively, you can right-click on the project's name, choose "Edit" and change its name.