For those who doesnt read comments
you can simply achieve that defining a new style with Theme.Leanback.VerticalGrid as parent and setting item browseRowsMarginTop to any dp value you need. Then set this theme for the Activity implementing the vertical grid view. – fasteque
It helped me.
style.xml
<?xml version="1.0" encoding="utf-8"?>
<resources>
<style name="AppTheme" parent="@style/Theme.Leanback"></style>
<style name="NoTitleTheme" parent="@style/Theme.Leanback">
<item name="browseRowsMarginTop">5dp</item>
</style>
</resources>
AndroidManifest.xml
....
<activity
android:name=".stackedadprogram.StackedAdProgramActivity"
android:exported="true"
android:parentActivityName=".launcher.ProgramDetailActivity"
android:theme="@style/NoTitleTheme" />
....