Hi,
I'm afraid that's not possible.
In my tests, I added a single radio button, Managed, and applied field-level security to make this button visible only to the administrator.
Then add a column change event to this button, by sending the webapi to change the statecode field of the form to 1, i.e. set the form to Inactive state, so that the form is not editable.
Then, add an onload event to the form where the Edit button is hidden if the Managed field is Yes and the currently logged in user is not the system administrator.
However, the system administrator cannot click the Managed button in edit mode to take the form out of read-only mode.
In summary, it is possible to click the button to make the form read-only, but it is not possible to click the button again to exit read-only mode.
Best Regards,
Dengliang Li