How to delete a file using the delete key
You can use Karabiner-Elements  with a modification rule imported from here:

The following custom rule that maps Delete to Cmd+Backspace:

~/.config/karabiner/assets/complex_modifications/_finder_custom.json

{
  "title": "Finder Custom",
  "rules": [
    {
      "description": "Use Delete as Move to Trash",
      "manipulators": [
        {
          "type": "basic",
          "from": {
            "key_code": "delete_forward",
            "modifiers": {
              "optional": ["any"]
            }
          },
          "to": [
            {
              "key_code": "delete_or_backspace",
              "modifiers": ["left_command"]
            }
          ],
          "conditions": [
            {
              "type": "frontmost_application_if",
              "bundle_identifiers": [
                "^com.apple.finder"
              ]
            }
          ]
        }
      ]
    }
  ]
}


Then open KE and on the Complex Modifications tab, push +Add Rule and then select your rule from the list.

The downside is that if you rename a file using finder and press the delete (forward-delete) it deletes the text from the cursor to the beginning.  

Another downside is that if you click a file on your desktop and try to rename and use the delete key to delete some of the filename text, it deletes the file.  While I still have this modification in place I do find I am having to remap my brain to use the backspace key when renaming a file and deleting a portion of the text.

https://github.com/tekezo/Karabiner-Elements/issues/1081