Please help us to promote this ticket to prioritize fixing:
Currently ToolbarItem hardcoded to use icons from resources. See the source code: https://github.com/xamarin/Xamarin.Forms/blob/master/Xamarin.Forms.Platform.Android/AppCompat/NavigationPageRenderer.cs
It's possible to draw custom icon (we prefer NGraphics, but native canvas is good to) but it's hard to use it. ToolbarItem can load icons ONLY from Resources.
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