If you are certain that a Chrome window is already opened, and you do not want to open a new one, set Open=Never.
If there’s no specific window you want to attach to, but just any, you can omit the “title” part of the window’s selector.
To open a new tab, you can try sending hotkey Ctrl+T, or by injecting JS (How to open new tab of the same browser - #3 by Yoichi)