How do read data from the app loader

Replace 'gpspoilog.csv' with 'setting.json' because that file surely exists. But with the download button I get no data.

Ahh - this is your issue I think. There are two different types of file on Bangle.js:

• Normal files of a fixed length created with require("Storage").write
  
• "StorageFile" files created with require("Storage").open which can be appended to
  
  

You're trying to load the first type (setting.json) using code meant for the second type (gpspoilog.csv).

Try using Util.readStorage("setting.json") instead and it'll probably be fine (the code normally used Util.readStorageFile)