The best way to learn something with Programming/Designing is trial and error. Just practice by making other things.
I looked at Jes00's basic GUI editor but I want to learn more, specifically how to add elements to the GUI easily, and programmatically.
The gui editor wasn't created by jes00
Try the Torque 3D official GUI tutorialhttp://docs.garagegames.com/torque-3d/official/content/documentation/GUI%20Editor/Tutorials/Firstgui.htmlInstall torque 3D and use their GUI editor. Much better then the BL one...
who says everything will be compatible
specifically how to add elements to the GUI easily, and programmatically
it's literally just torquescriptguis are objects, you can make stuff