Support multiple items in a single source file

**Is your feature request related to a problem? Please describe.**
As an functionista, I'd like to bunch bags of lil' functions together in a single source file.

**Describe the solution you'd like**
If you edit something that comes from a multi-file, you see the entire multi-text. Insert a new item and it gets defined and saved as such. Remove an item from a multi-text, it gets deleted and the file updated.