I want to create a scratch mod similar to blue baritones Early Scratch 3 Prototype
Look through my code. That's how I figured it out.
Which file its sooooolong
If you esnt to creste a scratch mod, then you need to use node.js, because scratch 3.0 uses node.js (you can tell if it invluds a package.json file). The only way to not use node.js is through a very very long process of downloading all the packages used, and figuring out how to make them all available. Overall, you're much better off just using node.js, as that builds scratch for you, and helps keep the libraries up to date.
Anyway, this is not even the right forum to be discussing this, as this forum is for snap, not scratch. Plus, jens doesn't like it when users talk about javascript here, especially javascript that is not related to snap.
How would I use the node.js? And how does and why does scratch use node.js(I think it’s for the compiler and events)
The simple answer is, google it. There are far better resources about setting up node.js than if I put the instructions here. You may also want to ask in the scratch addons discord server (found on the scratch addons website), as there are people there better qualified to answer questions about modding scratch than there me (and this forum is not the right place for discussing stuff like this).
I used a really old version of Scratch 3 that wasn't ever publicly used as the base for my mod.