Hello Mary and thanks for the advice.
The SD folks actually already have separate accounts for their student and employee personas, but the 'managers to categories' suggestion has definite possibilities. Thank-you.
No, wait. This would involve adding each SD account to each category, no? (Well, the top-level categories anyway.) That may or may not fly. But worth considering anyway.
Just thought of another hitch: What if two SD staffers are each taking a different Moodle course. We'd have to set up two additional categories and add all-but-the-student-staffer to each category. Getting more complicated to maintain...
There's gotta be an easier way.