How to programatically close a child dropdown

[therealsujitk]

Say I have a multi-level dropdown, I'd like to programatically close the child dropdown while keeping the parent one open. Trying to do it this way but for a variable bound to the second dropdown just closes both of them (I'm guessing this happens because the focus is lost).

Would love to hear any ideas on how to do this, additionally I'd also like to open a child dropdown programmatically, i.e. on button click it opens both the parent dropdown and the child dropdown at the same time (it should also support opening both individually).