There are examples in the tutorial, including a circular linked list.

You can just store all them items of the list/tree/whatever on the stack, growing it as needed, or you can add an addition "freelist" for a particular stack, so you can re-use items.

At the end of the day trees are still stored linearly in memory. Think of it as an array, with each node an element of the array, and indexes used rather than pointers.

Plenty of trees only ever grow. And that's the normal type of array in Goose. However you can also have arrays that can grow and shrink, if you have a tree that is constantly in flux.

Either way it'll be one stack for an entire tree.