As I’ve explained before, the App.openDoc() method will always open a new window for the document, there is nothing you can do about this. As far as I know, you cannot open a document using the same window as the current document via JavaScript, this can only be done using a real link (or bookmark) that is using the « go to page view » action.
Si c’est KHK qui le dit on peut le croire.
Mais on ne peut pas lancer une Action depuis un signet, on ne peut lancer que du JavaScript.