If you try to specify icon layout in taskbar via GPO you are able to use XML file according to MS schema (https://docs.microsoft.com/en-us/windows/configuration/customize-windows-10-start-screens-by-using-group-policy).
One thing that bothered me was that from total of 4 icons only 3 applied. And reason was pretty simple.
Although Windows is fine with using Forward Slash, Backslash and even both combined, in this case only working scenario is BACKSLASH.
<taskbar:DesktopApp DesktopApplicationLinkPath="%programfiles(x86)%/Google/Chrome/Application/chrome.exe" />
Not working
<taskbar:DesktopApp DesktopApplicationLinkPath="%programfiles(x86)%\Google\Chrome\Application\chrome.exe" />
Working