As you know, Thunkable X does not allow offline full data exchange between the WebViewer and the native part. For this you have to use Firebase, which allows you to get fast data exchange. There is also a method of slow data exchange without using Firebase, one of the variants of which is given in the basic example.
https://x.thunkable.com/projects/5bcda40fc3c5f0331502e40a/project/properties/designer
Web Injector - demo project of data exchange between the web and the native part.
https://x.thunkable.com/projects/5bced1cf04fbbda02f35ffd3/Screen1/designer
Another demo project. That’s how exciting the application interface would be if Javascript were available in Thunkable X for exchanging data between a WebViewer and an app.
https://x.thunkable.com/projects/5bdda7b698d675c41aefe129/project/properties/designer/