I once saw a JavaScript bookmarklet on the internet, but I lost it.
The bookmarklet does not specifically enable/disable the page editability, but it does toggle the editability, meaning that pressing the exact same bookmark turns editing on (enables) if it is currently off (disabled), and vice versa.
What was the bookmarklet script?
best way to turn it off easily would be to just create another bookmarklet, except change 'true' to 'false.'...or you could use this convinient toggleable bookmarklet
source: https://gist.github.com/jameswyse/b5b9f42bf38e7c09262cb37ea44ce626