A good Zettelkasten is both horizontal and vertical

A good [[Zettelkasten]] is both horizontal and vertical.

The main compartment of your zettelkasten, where the entirety of your single-idea notes are stored, has the potential of becoming a very unruly place. Without high-level views to make sense of your sense-making, thousands of notes may eventually feel like a disorganized mess

– [[A System for Writing]]

See also: [[Neither Vertical Nor Horizontal]] for similar approach to structure and organisation in a political context.