[ifethereal]

One example of a data structure implementing faceted classification would be the multitree [0]. Unfortunately multitrees seem to receive far less support than 2 other data structures it intermediates: trees and DAGs.

k-d trees [1] are close but use cases seem to predominantly target data with inherently ordinal (rather than nominal) dimensions.

Further abstraction could lead to the knowledge graph [2] or graph databases.

In all cases, the availability of "low-code" tools (in the domain of single-user personal information management, at least) seems sparse. I have been looking for some time, but the search continues.

[0]: https://en.wikipedia.org/wiki/Multitree

[1]: https://en.wikipedia.org/wiki/K-d_tree

[2]: https://github.com/JeffreyBenjaminBrown/hode

[chrisweekly]

Graph-based PKMS have recently exploded in popularity and sophistication. Athens Research (the OSS counterpart to Roam), and especially ObsidianMD (with its plugin ecosystem) are a couple examples of systems that might suit your purposes well.

[jimmySixDOF]

rea.ch is a new Graph based PKMS that addresses some of the same issues so everything from File tagging to notes association as part of a second brain/zettelkasten schema.

[1] https://rea.ch/

Edit: I should also give a shout out to Treeview for Twitter which let's you select between different tree visualization of Tweets.

[2] https://treeview.ml