I had the same issue (Generating/ changing JSON object - #12 by drted). The solution I originally created worked EXACTLY like dictionary blocks in App Inventor 2.
Unfortunately, Thunkable changed variable handling in some way in April/May, causing my recurrsive functions to no longer work. I have a second version that works using a loop instead of recursion. The block “Syntax” is a little clunky now, but at least it works for both GET and SET. The working project is here:
https://x.thunkable.com/copy/19b2ea706648f806f2ccf5e5eecb1e01
