The custom_data module demonstrates how to define and access custom configurables, how to embed files in a module, and how to overlay files using embedded files.
Build it from project "customDataDemo".
After loading this project on your device, you will see a "Custom Data" tab at the left in the Web Manager. Hit that tab, and you will see a "Custom Device Configuration" page. Bring up the Trouble Log on a Line to watch what is happening. Change "Name", "Rank", and/or "Serial Number", hit submit, and see the changes come out on the Trouble Log.