I'm new to ODK Central. After I create an entity, sometimes I want to go back and rename a field, but I cannot find a way to do that. Also, I want to rename or remove the entity for some reason, but I don't know how to do that either. Could someone give me a hint on how to do these simple things?
That is possible through the Central interface. When looking at the table of Entities, hover over a row and click on the trash can to delete or the pencil to edit. If you don't see these functions, you may need to upgrade Central.
For Entity properties, you're right that there's no way to delete or update them through the Central interface. That's because properties have links to forms and other resources and deleting and renaming them is not always safe. You can modify them through the database at your own risk but may run into unexpected behavior if, for example, a deleted property is still updated by a form. We do eventually intend to add functionality to delete properties but it's not as easy of a problem as it may seem!
That version should allow you to delete individual Entities! If you click into the Staff list, you should be able to get to the data table and see what I shared in my screenshot.