Categories in AGOL and now Portal 10.6.1 are looking like an excellent enhancement to help users quickly discover data, maps, scenes, apps, and items. However, Categories seem a bit disconnected from the concept of an item's metadata. There is no implemented metadata element which stores Categories. We are looking to add the Categories values as tags and they will then be included in the metadata. But think that a specific metadata element for Categories would be better to keep track of them. As tags, it would require manual synchronizing tags and Categories and would be best if better integration of Categories with Metadata was implemented in AGOL and Portal.