Computer Configuration > Administrative Templates > Microsoft Edge > Extensions
Both
HKLM\Software\Policies\Microsoft\Edge
Lets you specify which extensions the users CANNOT install. Extensions already installed will be disabled if blocked, without a way for the user to enable them. After a disabled extension is removed from the blocklist it will automatically get re-enabled. A blocklist value of '*' means all extensions are blocked unless they are explicitly listed in the allowlist. If this policy isn't set, the user can install any extension in Microsoft Edge. Example value: extension_id1 extension_id2