UI: Editor mode JSON input need for user to save changes not clear

The main JSON input of the editor mode UI requires a user to separately press a save button after changes. Given the size of the input on the page and the placement of the save button, it is easy to forget or miss the need to press this.

Given that the input is a top level part of the UI, it doesn't seem like there is a need to save and close as with many of our dialogs and forms.

Potential improvements would be to try and make the 'pending change' status of any inputs in the JSON editor more clear with some styling, or maybe to make the save button more prominent, or even to remove it for this input and have changes here be reflected as the user interacts with the input.