Problem: you are looking for user-exit for transactions QA01/QA02/QA03.

Solution: what you are looking for is a SMOD project called QPL10004.

There are two function modules in this particular enhancement. First one, called EXIT_SAPLQPL1_004, will allow you to transfer data to custom fields on the screen. Second one, called EXIT_SAPLQPL1_006, will allow you to transfer data from custom fields on the screen and save it in the database or process it in any other way.

There is also an include structure called CI_QALS which will allow you to add new fields to the QALS database table.