I've made a new tool. The name is 'GCT Fusionizer'. Don't laugh xD
This is the tool. It's quite simple and easy to use:
And what does this thingy?
Well, it copies the data from a gct file to another. So, you have the previous codes AND the new ones. There's no control about the codes added, if they're repeated or something. It's just what I've said, a program to add ocarina codes from one file to another, nothing more.
The source gct must to be named 'code.gct'. The files to be overwritten are named either RSBE01.gct or RSBP01.gct. If you have both in your folder, you can select. You can also add the codes to both at once, but that's not something that's supposed to happen, as pal and ntsc files aren't usually (if ever) compatible.
The normal use would be compiling something you lack in your usual gct in a separate file, and then use the Fusionizer to add the new code to your file. As the program doesn't make any backup, just be careful and keep always one copy of your original files.
I've made this thinking on the alternate stage loader codes I want to include with Peach's Castle, and how easy will be adding them to already made gct files by just using this tool.