Are there any arrays?

I understand that they can be written with the help of code, but suddenly there are ready-made libraries with blocks. Or will i have to write in C ++ and then make the library myself??

nth-input (and to a lesser degree select) nodes provide similar indexed-lookup functionality.

is that like the variadic nodes?

It is one example of a variadic node. Variadic node is one that can change number of input pins by dragging the tab on the right of the node.