In Visual studio there is no support to create App icons for cross xamarin platform projects or I have not found it yet. You need in Android project 13 different sized icons, in iOS 18 different sized and in UWP 27 different sized icons all in png- format. In Android and UWP I have investigated the usage of this many icons in a way, that I have numbered each and look into the application of apps in emulator or real device. The result is available in this document App-IconsUS-V1.pdf. If you want to repeat this experiment, use these both zip files to get the numbered icons and put them manually into your project: Numbered Androis icons and Numbered UWP- Icons.
In the above mentioned document App-Icons I have presented a simple Windows- Forms program ResizerBay I have found on Github here and improved it a little bit with adaption to the latest version of cross platform xamarin forms projects. Thanks to Mr. S Ravi Kumar. With this program you can load your designed icon and the program automatically can produce all necessary 58 icons with correct sizes and names and folders. Look for the executable program ReSizer.exe in the bin/debug folder or start the solution file ReSizer.sln. After running this program you have of course to manually copy the resulting icons into your cross platform project.
At this time I have not solved the Android adaptive icons. My icons produced with the Resizer are located in Android version 8 or 9 within white circles. So I am wor
king on a solution. I guess I have to go to the native Android Studio program from google and design the background behaviour of my foreground icons.