@steanne’s answer above is correct.
Here’s a detailed tutorial. After following these instructions, you’ll observe the following:
- The Super keys (when pressed alone) open the Whisker menu, just as they do now.
- Other keybindings with the Super key (like Super+E and Super+D) work as expected and do not open the Whisker menu.
First, install xcape:
sudo pacman -S xcape
Next, in the Session and Startup app, go to the Application Autostart tab and add this autostart task:
Name: xcape
Description: Map Super Keys to Alt+F1
Command: /usr/bin/xcape -e 'Super_L=Alt_L|F1;Super_R=Alt_L|F1'
Next, in the Keyboard app, go to the Application Shortcuts tab and remove both of the xfce4-popup-whiskermenu shortcuts (both Super R and Super L).
Still on the Application Shortcuts tab, add a new shortcut:
Command: xfce4-popup-whiskermenu
Then click OK. When prompted for the shortcut key, press Alt+F1.
Finally, log out and log in again, and you’re done.