In the original designs for the new link UI in the Nav Block, @shaunandrews included Categories in the search results. This was descoped to allow teams to focus on returning Pages (the primary use case).

This Issue documents the originally suggested featured for posterity. It may well be that this isn't deemed desirable, but it helps to have a record.

Describe the solution you'd like
(If desired) When searching for an existing entity in the Link UI within the Nav Block, the results should include not only Pages but also WordPress Categories.

Note that currently, the Nav Block returns only Pages from the Core REST API search endpoint.

However, adding this feature doesn't necessarily require customising the Search endpoint in Core.

We could also explore the idea of adding another query into the __experimentalFetchLinkSuggestions within Gutenberg and then combining the results before returning them to the Editor data store.

Describe alternatives you've considered
Not including Categories at all. It might be too much and very much a secondary use case.