macOS - Difference between /Library/Preferences/ & /Library/Managed\ Preferences
Managed Preferences were used by Casper Suite (now Jamf Pro).
According to the Casper Suite Administrator's Guide v9.97:

Managed Preferences are manifest files that define preferences for computers and users. You can use the JAMF Software Server (JSS) to create Managed Preference profiles, which contain groups of Managed Preferences. You can also specify the users and computers for which a profile should be applied (called “scope”).

But Managed Preferences has been removed since Jamf Pro 10.0.0:

The following functionality has been removed:
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Managed Preferences—Support for managed preferences has been removed. It is recommended that you use macOS configuration profiles to define settings and restrictions for computers and users.

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They were based on the now deprecated Managed Client for OS X (MCX).