Cannot save changes to a JSON table

Hello, more detail? You read the data in the query right? and save it to variableTableJSON, then refer it with {{variableTableJSON.value}} in table data source?

I think you are write your first app.
here is a docs for your refer

https://docs.retool.com/apps/web/quickstart

you also can export app to json to us to check, thanks.

or maybe this topic is helpful for you.