Discovery is fundamental in your personal book of knowledge. The easier it is to discover what is in your PBOK and what interconnections are in your PBOK the more valuable your PBOK is.
In a digital PBOK, there are four mechanisms for discovery.
You can discover information by traversing links from one note in your PBOK to another note. The form and structure of notes will make this process more effective.
You can discover all the notes that have no links, typically called orphans. Best practice would be to add links to or from these notes when they are discovered.
Notes can be discovered by the hashtags that are associated with the note. The better the taxonomy of hashtags the more effective they will be in discovering notes.
Finally there is searching by text. This is the least effective method as there can be no structure or taxonomy related to the text.
When adding new information to your PBOK, always add it with an understanding of the ways you will retrieve it at a future point in time.