How can I expand/collapse a list?

[vaaleyard]

I'm trying to create a ListItem and I'd like to expand/collapse some elements of this list.

For example, in the image above, all items starting with ">" are the ones i want to collapse/expand (specifically when the Enter is pressed), how can I start doing it?

I already know which items are menu, all the "true" in the right side, but I have no idea how I can hide all the items below the corresponding menu. I think a BtreeMap is the best fit here to create the list and his childs, but the help I need is how can I hide them?

Just a tip to help me get started.