If I understand you correctly, you need to create new Sub-Discipline categories. To do this, click on a drafting view you want in one of your detail categories. In the Properties dialog, look for Discipline and Sub-Discipline. Discipline should be set to Mechanical (for Mech details of course), and you can type in whatever you want for Sub-Discipline. Once you have typed something in, it's available in the drop-down menu, so you don't have to type it in for every view.
You might consider opening another project with this already set up, so that you can make the Sub-Discipline names match. Consistency is extremely helpful in maintaining efficiency and avoiding confusion, especially if others will be working on the project with you.