I have received a response to my ticket. Essentially they informed me that locking a note to make it readonly is not possible currently and it may be implemented in the future.
In response to some of the recent posts, please bear in mind we not requesting some sort of AI DeepMind type of feature that requires 1000's of man/scientist hours - no - simple flag on a note to indicate its locked. Coming from software development background myself, it seems almost laughable that this is not implemented after so many years. Which is why I feel there is no real attempt by EN to listen to their customers.