The only thing the 1.16 hacked editor has over this new one was add/delete buttons.
Go to the drop down on any tab in the un-hacked 1.17 editor. Choose something and make that bar highlighted. Now hit tab to move the box to the rename button.
Now you can hit "A" to add, or "D" to delete. Essentially, the 1.17 editor is hacked.
Note: I learned this from someone else. That person gets all credit for this discovery