Don't think too much about the publish date. It's possible to make thematic layer groups in Experience Builder now without a Custom Widget. (Now meaning after the February 2026 ArcGIS Online update, Developer Edition 1.20, or Enterprise 12.1.) If your thinking I've written this post before, it's because I have, but seriously it actually works this time. You can read the linked article if you want. There really isn't any new information in this post except that it actually does what that build was meant to do now. Here's the critical info from that post:
I've grabbed basically every layer on that server that falls into these categories: Demographics, Natural Disasters, Animals and Cryptids, and I will try to make Experience Builder recognize these categories.
