Settings that alter other parts of the registry are called "Preferences". This behavior is called "tattooing". Changes to the registry will not be reverted back to their original state after a Group Policy does not apply any more.
The Group Policy Editor only shows Policies, not Preferences.
To resolve the issue, right-click the "Administrative Templates" node of either "User Configuration" or "Computer Configuration", choose "View" and "Filtering" from the menu. The "Filtering" windows opens. Uncheck both options at the bottom of the window:
"Only show configured policy settings" and "Only show policy settings that can be fully managed".
The Group Policy Editor should then show all settings from the custom or third party ADM template.
Article ID: 555934 - Last Review: 14 Feb 2017 - Revision: 1