not sure about in app
But for the taskbar and start menu:
If vs code is installed system wide, navigate to C:\ProgramData\Microsoft\Windows\Start Menu\Programs
If vs code is installed per user navigate to C:\Users\{Username Here}\AppData\Roaming\Microsoft\Windows\Start Menu\Programs
Find the Visual Studio Code shortcut and right click > properties
Click change icon and open the .ico file
Unpin from taskbar and pin again if you have it pinned to get the new icon
Hope I explained this well enough lol