Cinnamon: How to position popupmenu?

I'm new to cinnamon desktop, I used gnome session fallback and mate before. What I'm trying to achieve is the following: when I right click on a window on the panel, the popupmenu should be right above the place I clicked. But for some reason the popupmenu is designed in a way that its left corner is positioned to the center of that window switcher thing. But I'd like to move it to the left side.

So basically:

I think it could be done by editing popupMenu.js but I'm not sure how. I didn't find anything relevant in css files. Any thoughts?

(I'm on ubuntu 16.04, cinnamon 3.0.7)