Disable Forget Button
Supported on: Firefox 60 or later, Firefox 60 ESR or later
Registry
HKLM
Software\Policies\Mozilla\Firefox HKCU
Software\Policies\Mozilla\Firefox Value name: DisableForgetButton
Enabled: DisableForgetButton = 1
Disabled: DisableForgetButton = 0
Description
If this policy is enabled, the "Forget" button is not available. If this policy is disabled or not configured, the "Forget" button is available.