You should link your notes
It is not the amount of knowledge that makes a brain. It is not even the distribution of knowledge. It is the interconnectedness.
You probably write a lot of notes already, and already have Reasons to write notes. What might not be so obvious is why you should link your notes together. Maybe you've seen a lot of hype about Roam Research, Zettelkasten, Obsidian and don't get why. Here are the reasons I link my notes, regardless of app.
Links multiply reuse, and prevent abandonment
Even without links, I would re-read and refer to old writing. An old resume I would use as a basis for a new resume. An old report that got rave reviews I can re-purpose to make a new report. A snippet of code that I knew to work and would want to use again, but too small to warrant an entire version control system.
Without links, how many times a note got re-used tended to be limited. It's too much work to continually create new folders for notes, then crawling through those folders to look up a note to reuse it. Subconsciously I would use notes less and less, or even completely forgetting that they exist at all. I suspect the latter is extremely common, and undetected because it is extremely hard to realise that you have forgotten to remember something. This is a strong limitation of folders as an organisational structure, where files can only exist in a single folder. Such files put in deep folders became abandoned, never looked at again, with great regularity.
With links, I can access a file in a single click instead of twenty, which means I've found that I reuse my work perhaps 10-100 times as much as I did before. There is surely still some number of files being abandoned and forgotten, but they are far fewer now.
Links refine my writing
The reuse of my writing as a result of linking has meant I've been strongly encouraged to refine it in many ways. The simple act of linking by itself forces me to look at a note's title, encouraging me to carefully rewrite the title for better reuse. Reusing a note a few times encourages me to fix simple errors like spelling and poorly formed sentences. Some amount of more reuse encourages me to format lists, and add a hierarchy of headings. A great deal of re-use encourages me to find contrasting arguments, supporting links, images, diagrams, videos and more.
This increased quality of writing has directly contributed to my professional success and personal development. When you are the one person on a team who can write, you can lead. Technical writing is required for Engineering Leadership.
Links make writing fun again
Someone described my writing app of choice, Obsidian, as like playing your mind like a videogame. I have found this to be true. The activity of just creating links between documents I've written is incredibly satisfying, even without the visceral visuals and sound effects of a videogame. Creating a working link that clicks through to valuable content on the other side has no equal.
Additionally, it allows exploring my writing through a bouncy graph visualisation, which is so much more fun than plain text.
My conversations flow better
Many of us have had the feeling of thinking of the perfect punchline long after the conversation has ended. The French call this going down the stairs. I theorise that if you're too slow in conversation, you can become faster if you do reps of linking your thoughts together, in the form of linking notes together. Some argue that this is done better with spaced repetition, with flash cards prompting one reply, but I feel that is too rigid. In contrast, linking many notes to many other notes allows much more freedom, which is essential for flowing and unstructured conversation.
Links in journals give the illusion of superhuman memory
In my Journal, I would write about the daily goings on, and in each snippet I would link to things. That could be something totally mundane, like:
Mr Smith helped Mr White with the Deployment of Our secret app.
I have written thousands of these little notes, as they happen. Later, when asked about what a person had done, I could use these links to remember what had happened, even better than that person could themselves. This gives the impression of truly superhuman memory, memory that can't be reproduced by a flesh brain.