Yes, knew that of course, I tried it like this:
<splash src="/res/android/screen/splash-port-xhdpi.png" density="port-xhdpi"/>
<icon src="/res/android/icon/xxxhdpi.png" density="xxxhdpi"/>
where the rest of the content is created by “Android App Configuration” in Monaca.
Just adding my line to the end (and uploading the png to that folder) doesn’t work.
I saw some examples searching online, but they use a different folder-structure then is created by Monaca (like Android Asset Studio Notification icon generator).
(My goal is for this https://github.com/fechanique/cordova-plugin-fcm plugin to show a different icon for the statusbar notification as stated there:
"For Android >5.0 status bar icon, you must include transparent solid color icon with name 'fcm_push_icon.png' in the 'res' folder in the same way you add the other application icons. If you do not set this resource, then the SDK will use the default icon for your app which may not meet the standards for Android >5.0."