I have been using JSON Buddy to alter the GDevelop Files (not the .js code).
It has been particularly helpful in building new scenes based on the templates built from previous scenes.
This is particularly important for me based on my reliance on Global Variables.
In GDevelop duplicate one scene (make sure it is the last Scene in the list).
Then open the json file in JSON Buddy and search for the duplicate scene name.
It should have mangled name near the find to indicate the start of the new scene.
I use prefixes on all my variables and objects, so I can then just do a find and replace of the prefix to create new variable/object names and update the code accordingly.
When the replace gets to the end of the window hit no, so you don't replace through the previous scenes.
Before you close JSON Buddy move to the text view window and go to the JSON Menu and select Remove White Space.
Save as a new file name and open in GDevelop to test your newly created scene.
On top of that JSON Buddy seems to be the best solution that I have found so far in actually helping me understand the nitty gritty of the GDevelop code a bit more.
Hope I have explained the process in an understandable way and that it helps some of you save some time coding.