It has become a passion of many people to create the maximum number of notes, organize and interconnect them to the maximum degree.
Apart from the beginning, there is a key area within the NHS link you provided.
At the beginning, it states that:
A hoarding disorder is where someone acquires an excessive number of items and stores them in a chaotic manner, usually resulting in unmanageable amounts of clutter.
You said the notes are arranged and interconnected.
The NHS page also says:
What's the difference between hoarding and collecting?
Many people collect items such as books or stamps, and this is not considered a problem. The difference between a "hoard" and a "collection" is how these items are organised.
A collection is usually well ordered, and the items are easily accessible. A hoard is usually very disorganised, takes up a lot of room and the items are largely inaccessible.
For example, someone who collects newspaper reviews may cut out the reviews they want and organise them in a catalogue or scrapbook. Someone who hoards may keep large stacks of newspapers that clutter their entire house and mean it's not actually possible to read any of the reviews they wanted to keep.
What you have described is a collection of notes, organised and linked up as much as possible. That is not hoarding as described by the NHS.