How to export Android Signing Keys

To locate the key to export, find the file first in this path:

On Windows (apparently):

X:\Users\username\AppData\Local\Xamarin\Mono for Android\Keystore

On macOS:

/Users/username/Library/Developer/Xamarin/Keystore/alias/alias.keystore

(Note, depending on how you signed the last time, alias may be the same as username, as it was in my case.)

So I simply copied the keystore file from that location over to the other OS. When importing it in Visual Studio (clicking the "Import..." button in the "Distribute" dialog), it asks you three things:

Password:
Alias:
Key password:

You cannot leave any field as blank! The password is the key password that you used in macOS to sign. The Alias is the name of the file without the .keystore extension, and the "Key password" is the new password that you may want to use for Windows (I left it as the same as in my macOS, myself).

In my installation every release keystore is stored at X:\Users\username\AppData\Local\Xamarin\Mono for Android\Keystore\AppName
Check also here

If you are looking for self generated Keystore path,

Right click on Keystore Name -> Show Alias Info -> at bottom you will see path of self generated Keystore