When you save a script the entire app is saved, but data is not automatically reloaded.
When the script is saved, the app will still contain old data from the previous reload, which is indicated in the toolbar. If you want to update the app with new data, click in the data load editor toolbar. The script is automatically saved to the app when data is loaded.
Data load editor saves your work automatically as you make changes to your load script. You can force a save by pressing CTRL+S.
When you save a script, it is automatically checked for syntax errors. Syntax errors are highlighted in the code, and all script sections containing syntax errors are indicated with next to the section label.