How to enable the 'super' key?

The keybindings you show in your Window Manager screenshot work for me. However, I first had to perform the configuration described in this post:

Edit: In newer installations of EndeavourOS, the steps above are no longer necessary. Instead, the Super key is pre-configured to open the popup Applications Menu (same as Alt+F1) and the Super+Arrow (Keypad) combinations tile windows.

Revision (2023-04-06):

I have rewritten my instructions for modifying Super key functionality so that they work with the latest offline installations of EndeavourOS: