Cannot find Library/Managed Preferences in macOS big sur

Kind of a vague question, since there are many permutations of 'managed', but in general, the system is 'managed' for a reason, and someone controls the management console. Speaking to that person, or knowing their password/access control, is probably key.

Managed systems exist for a reason, usually based on a legal, compliance or security basis. it wouldn't mean much if the regular user could simply bypass the controls at will.