Let’s make that all transport requests will belong to a certain logical group(project).
Also, it allows prohibiting the release of requests for certain projects.

1. Transaction SPRO_ADMIN. Let’s temporary close releasing of transport requests attached to a project.
   Create several projects:
   
   Go to the project > Transport Requests > CTS project status switch:
   
   Select “All configured transport targets”:
   
   Change Status Switch for Project:
   
   After that, no one can release transport requests attached to this project:
   
2. Transaction SE03
   Go to Display/Change Requests Attributes:
   
   Change “SAP_CTS_PROJECT” attributes:
   
   Change to “Mandatory”:
   
   After that, no one can create a transport request without specifying a project.