Computer Configuration > Administrative Templates > Microsoft Edge > Extensions
Both
HKLM\Software\Policies\Microsoft\Edge
Setting this policy specifies which extensions are not subject to the blocklist. A blocklist value of * means all extensions are blocked and users can only install extensions listed in the allow list. By default, all extensions are allowed. However, if you prohibited extensions by policy, you can use the list of allowed extensions to change that policy. Example value: extension_id1 extension_id2