How to access symbol on main timeline from nested symbol

I did read the the edge JSAPI but still no way to make it work.

Very simple use: you click on a button, a window appears. the button that makes the window appear is supposed to hide some elements which it does. HOWEVER when I want to use a close button within the symbol (window) to make these symbols appear again, it doesnt work.

From inside the symbol I tried:

sym.getComposition().getStage().getSymbol("openTabButtBlack").show();

Doesnt work.