apps/fxlab/app/src/main/res/menu/toolbar_menu.xml

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">

    <!-- Add a mute toggle action to our Toolbar-->
    <item
        android:id="@+id/action_toggle_mute"
        android:icon="@drawable/ic_baseline_audio_is_disabled_24"
        android:title="@string/action_toggle_mute"
        app:showAsAction="ifRoom"
        />
</menu>