<?xml version="1.0" encoding="utf-8"?>
<resources>

    <style name="Widget.Sample.Toolbar" parent="@style/Base.Widget.Sample.Toolbar">
        <item name="android:elevation">8dp</item>
        <item name="android:outlineProvider">bounds</item>
    </style>

    <style name="Widget.Sample.Toolbar.Transparent" parent="@style/Base.Widget.Sample.Toolbar">
        <item name="android:elevation">0dp</item>
        <item name="android:outlineProvider">none</item>
        <item name="titleTextAppearance">@style/TextAppearance.Widget.Sample.Toolbar.Title.Transparent</item>
    </style>

</resources>
<?xml version="1.0" encoding="utf-8"?>
<resources>

    <style name="Widget.Sample.Toolbar" parent="@style/Base.Widget.Sample.Toolbar">
        <item name="android:elevation">4dp</item>
        <item name="android:outlineProvider">bounds</item>
    </style>

    <style name="Widget.Sample.Toolbar.Transparent" parent="@style/Base.Widget.Sample.Toolbar">
        <item name="android:elevation">0dp</item>
        <item name="android:outlineProvider">none</item>
        <item name="titleTextAppearance">@style/TextAppearance.Widget.Sample.Toolbar.Title.Transparent</item>
    </style>

</resources>
Edit default shadow of toolbar to 4dp
Edit default shadow of toolbar to 4dp
