Uses of JohnDoe in the title, text, and tags fields of a tiddler appear when searching. Uses in other fields, however, such as the family field on JaneDoe, do not.

Later on, we'll learn some ways around this. In the meantime, it's good to keep in mind that user-defined fields are in many ways second-class citizens in TiddlyWiki. If you want to do much with them beyond creating them, you have to add those features yourself with plugins or custom logic. This is not to say that doing so is difficult, though!