A patch for the GUI scaling article is incoming!
Check out the new section that covers a workaround for built-in controls! Styleboxes and 9-patch textures are still in need of a solution, but icons — icons are simple to fix now
https://humnom.net/thoughts/67b7374e-the-simplest-way-to-scale-ui-in-godot.html
The demo project has also been updated with new tricks
There is also a very relevant discussion over at the Godot proposals repo:
https://github.com/godotengine/godot-proposals/discussions/9080
And it's where I got an inspiration for the new technique too