I made an icon that is an empty square with a black border for use in testing that I’ve occasionally found useful for other things.
It goes in an ICONS folder next to (not in) the addons folder.
This is the link: https://www.mediafire.com/file/cofe3xb90ej73jb/Empy_Icon.tga/file
All you have to do is drop it in the ICONS folder (make it if it’s missing) and restart your game client (not just relog).
It’ll show up in your list of macro icon choices.
One thing I use it for is blocking out buttons on my on-screen button bars that are not for use as “actions” (like my WSAD array).
I do that because I arrange my buttons on screen to match the physical layout of the buttons on the input devices I use to aid in translation between availability of an action in game and implementation of that action on my devices.
Here’s an example of them in use. The “empty” icons are so I can both see where the buttons are in relation to the rest of the devices involved and what slots I still have available to me.
https://www.mediafire.com/view/jgv7z7kek2p1sc5/What_I_Do_With_Empty_Icons.png/file