condition is : But it is not fixed how many lists of sub lists there are
Select main list item 1 on index 1 then show sub list 1, and when click sub list 1 of index 1 then show sub list 2 and continue … last final get item list
if main list have not sub list then show item list (but remember condition of sub list as above)
If you are going to create a guide or provide this kind of advice, it should be clear and easy to understand. You should also provide an example with screenshots of the UI, blocks, and final output.