Just got my slack upgraded to 13.1 and (of course) Warcraft 3 fad issues acting strange when ALT+Tabbing. So here is what i did to get things back on wheels:

First: Find this settings panel (Personally got some issues finding it because in settings menu there seems to be difference when browsing in tree mode and in icons, so -> use icons mode )

Second: use the "Detect Window Properties" button to get valid window recognition

Third (last): The main issue was the pannels acting weird when war3 was minimized, so to get this one fixed your pannels have to be set to "Always visible.

Here are screens of my settings. Guess they are quite enough

Panel1.png

Panel2.png

Panel3.png

Panel4.png

Panel5.png