Portal Problems

I wanted to ask how I can manage to not let a Nether portal go into the default nether world but into a completely new Nether world that I have created with a command. I just wanted to ask how I can turn world a nether portal into test_nether and this also with the End_Portal.
With best regards

I think this is possible with the multiverse plugins. Using those you can create new worlds and also change wich worlds are linked, for example in your case you could group those worlds and when you go trough a portal you end up in your desired world. I recommend checking out some turtorials for multiverse since it’s quit hard to explain myself.