When creating an article with Quick Content Creation, the option to select a category for the new article only includes the first 50 categories by alphabetical order. Searching a category beyond these 50 returns no results. In my world (Astra Planeta) the list stops at Space Exploration, and I was trying to place the new article into the Toliman category.
In a world with more than 50 categories, open an article draft. Then use the Quick Content Creator to make another article. Click the Category drop-down field. Search an existing category that begins with a letter from the end of the alphabet.
No longer relevant :)