"Tag types" as an alternative to nested tags

Currently, Obsidian supports tags as a recognized key in YAML frontmatter. Together with support for nested tags, this means we have an easy way to create different kind of tag hierarchies.

My plan is to start using at least one “system” parent, and one “type” parent.

But while this technically works, with nice nested tags in the tag panel, it’s not a solution that brings readability to the frontmatter.

Is there a way to use other keys in addition to tags, like source and type, and have them added to the tag panel?:

tags: [pkm, obsidian, zettelkasten]
type: [evergreen]
source: [book]