I havent seen any non-super outdated Datapack mergers. They also look kinda sketchy, but maybe that's just me.
run the following commands in your terminal: pip install pillow pip install customtkinter
then:
look through the .py code(or not) and press run
If you are on linux, it should work because it's just python. If you are still having issues installing, follow these steps:
Step 1: get Windows
Step 2: follow the Windows guide above