I'd like to create a custom navigation for my site's Pages library. To do this, I'm going to organize the pages in folders, and have a few extra columns on the folders, such as a CSS class, display order, subheading, etc. I've created a new site content type, inheriting from the Folder content type. I've added the extra columns to the new folder content type, and I've added the content type to the Pages library. But when I try to create a new folder using this content type, I get a "Sorry, something went wrong" error.
Is it not possible to use custom folder content types in the Pages library? It works in a standard document library.