Customizing an entity in the front end. What happened to it?

I used to be able to add or override attributes for entities through the UI. I can see the changes that were made to configuration.yaml for the ones I modified long ago, yet I cannot for the life of me figure out where that UI is. Did it get removed?

Yes. Last year,

Okay. I missed that.

Once an attribute is created in the customize file, is there a way to manually change that attribute’s value from true to false on the fly?