Why didn't you use the section that is already there?
// Context Storage
// The following property can be used to enable context storage. The configuration
// provided here will enable file-based context that flushes to disk every 30 seconds.
// Refer to the documentation for further options: https://nodered.org/docs/api/context/
//
//contextStorage: {
// default: {
// module:"localfilesystem"
// },
//},
If you want to learn more, take a look at this thread: A guide to understanding 'Persistent Context'
