GUI Editor is a resource designed to allow creation and manipulation of GUI elements in-game, with the ability to generate the corresponding Lua code and output it to a file.
All credits go to R3mp for making this tool.
First of all, click here to download the resource.
Once downloaded, you must put it in the resources folder of our MTA SA as you do with other resources, but with a slight difference, this will be extracted in a folder:
When you go inside the folder it must look like this: