Hello! I made this script to combine the item Json files in Minecraft Java resource packs, the windows one I would recommend running in vs-code and for android you can run it in the below app:

https://play.google.com/store/apps/details?id=ru.iiec.pydroid3

NO ROOT NEEDED!

make sure the filepaths you input are valid

Just run and follow the inputs it will prompt you with, make sure when you give the item you want to combine you spell it correctly! EXAMPLE "diamond_sword" NOT just "sword"