while Running a Test Case or Creating TCER make Test Plan selection as Mandetory

Currently, there is no feature available to make the "Test Plan" field mandatory while running a test case. This behavior is part of the default functionality and cannot be customized at this time.

It comes under Enhancement (RFE). To ensure smooth execution and proper context when creating the Test Case Execution Record (TCER), we recommend always executing test cases directly from within the Test Plan. Doing so automatically sets the Test Plan context and associates it with the TCER during execution.