Haven't tried it, but I think it's this one. Had to dig a bit through internet and help myself with Google Translate because I know zero Chinese.
Project1论坛,这里主要有RMXP、RMVX、AGM、RMVX ACE的制作交流区,游戏素材分享区和原创游戏发布区,以及其他一些版块,适合游戏制作爱好者一起参与讨论,共同进步,交流经验,分享成果。 ,Project1
rpg.blue
But from what I can understand without looking at the full copy event code, yeah, it uses a data structure from another script. It seems to be some kind of cache for looking event data in order to create copies of events dynamically. Or something like that. And for some reason I can't infer, if the copied event uses switch 3, it will instead look if its current data was found, I guess? Again the copy event thing is part of another script. Even the post you mentioned seems to be someone looking on solving a different problem by using that script.