Here are some brief thoughts of mine on a feature that I have recently started to use: nested tags.
For those unfamiliar, they can be used simply by separating tag labels with a . (period) sign, e.g. bread.sourdough. This will not only make a tag in your collection for bread, but also make a tag for sourdough, wherein the note that these tags are affixed to will appear under sourdough (which will appear nested within the bread tag).
If categorization is your thing, this is very useful, especially is your working in a collection where any sort of categorized data needs to be more actively retrieved than if, for example, the category bread was instead recorded under a Note label like “Type” or “Category”. This structure is preferable when retrieval occurs when data is sorted through scripting and generating a desired output; or something like full-text searches in Notenik or elsewhere, I suppose.
However, I am of the view that nested tags serve as a good method to keep hierarchy/taxonomy in close proximity to the Notetaker within the Notenik interface.