What I've been doing with some of our problematic courses is to create trash quizzes and move categories with unused questions there - I'll be doing more of this as long as that option remains available (it will NOT be after the upgrade to Moodle 5 - cf. https://moodle.org/mod/forum/discuss.php?d=466039 and https://tracker.moodle.org/browse/MDL-84575 ).
Such operations slim down the course-level question bank and make it more usable.
My own approach to quizzes these days is - keep "shared question" to the necessary minimum. If there's a quiz that requires its own restrictive set of questions not to be shared with other quizzes, move these questions into the Quiz's local question bank.
PS. Sometimes, verifying whether a question is used or not can be tricky - cf. this "fix" https://tracker.moodle.org/browse/MDL-77625 ("Repeated quiz restoration to same course references original course questions"), which: (1) names the problem and aspires to prevent it from happening but does not cure pre-existing problem case unless you involve in deep-level manual fidgeting [which some of the discussion that ticket tackles]; (2) apparently spawned more problems than it solved. Ergo, I'm now waiting for this issue to be finally resolved - https://tracker.moodle.org/browse/MDL-83541 ("error_question_answers_missing_in_db when duplicate or restore quiz") - and will then decide how to proceed before the next academic year..
Such operations slim down the course-level question bank and make it more usable.
My own approach to quizzes these days is - keep "shared question" to the necessary minimum. If there's a quiz that requires its own restrictive set of questions not to be shared with other quizzes, move these questions into the Quiz's local question bank.
PS. Sometimes, verifying whether a question is used or not can be tricky - cf. this "fix" https://tracker.moodle.org/browse/MDL-77625 ("Repeated quiz restoration to same course references original course questions"), which: (1) names the problem and aspires to prevent it from happening but does not cure pre-existing problem case unless you involve in deep-level manual fidgeting [which some of the discussion that ticket tackles]; (2) apparently spawned more problems than it solved. Ergo, I'm now waiting for this issue to be finally resolved - https://tracker.moodle.org/browse/MDL-83541 ("error_question_answers_missing_in_db when duplicate or restore quiz") - and will then decide how to proceed before the next academic year..