This post is from the WWDC26 Web Extensions Q&A.
Is there an MDM solution that will give a Safari extension all the permissions it needs with no interaction from the end user?
Limiting user interaction when installing a Safari extension
Is https://developer.apple.com/documentation/devicemanagement/safariextensionsettings what you're looking for? It can be used to automatically enable an extension, and grant/deny website permissions.
Does this turn on the checkmark for the extension in Preferences? My impression was that it only gives the user the ability to enable it if they want.
Recommended
"State": "AlwaysOn" will make it so the checkmark is on and can't be turned off.
"State": "AlwaysOff" will make it so the checkmark is off and can't be turned on.
"State": "Allowed" will make it so the user has the choice to turn the extension on or off.