When you add context menu to the grid that is attached to DHX.Window then this context menu appears below Window.
I apologize for the delay with the reply.
Thank you for your report. The problem is confirmed. We’ll try to fix it in one of the future updates.
We have fixed your reported porblem with the context menu appeared behind the window.
You can test it here:
https://snippet.dhtmlx.com/kdk0md8t
Thank you for your report.