Content categories cannot be configured when external content has been disabled as part of configuring a disconnected deployment.

Workaround

Use the guide here to set Categories up via the Rest endpoint: https://developers.arcgis.com/rest/users-groups-and-items/assign-category-schema/

Note: If Categories are set up via Rest then the window will appear in the Portal to create more categories via Organisation > Settings > Items > Organisation categories, however if you remove all these categories then the page fails to load again.

Steps to Reproduce