Vanilla items into mcreator

I think it's not possible, like the default texutes, the code is copyrighted too, making it impossible to implement such a thing. Though you can see what plugins offer and have a look at the code for the totem through mcreator's ability to display minecraft's code

You shouldnt really need to use vanilla stuff as a template unless you are using the vanilla textures as a block (maybe your adding like obsidian door or whatever that you want compatible with texture packs)

Basically all of what you mentioned can be done by simply doing like 8 blocks of code. There is a way to show totem animation, way to remove items limit stacking, prevent player death, etc. If you are finding procedures too difficult then maybe work on random procedures until you get the hang of stuff (probably on a new workspace), then when you are comfortable come back and use procedures to accomplish what you need.