I use it to learn Chinese Pinyin. I recall whether it is correct or not by expanding and folding my notes. When the memory is correct, this note will be automatically moved to “all correct(全部正确)” without having to remember again.
An agent shows aliases of the original notes. Because aliases can’t have child notes an agent will always show a flat list, so what you’re looking for is not possible.
If you wish to view the text of the child notes of an agent, then you’d view the selected note in Preview. This affordance of an alias can come in VERY handy when writing complex reports.