Showing both movies and movie sets in a widget

As the title says, is this possible at all?

I created the following playlist:

<?xml version="1.0" encoding="UTF-8" standalone="yes" ?>

<smartplaylist type="movies">

    <name>Test2021</name>

    <match>all</match>

    <group mixed="true">sets</group>

    <order direction="ascending">year</order>

</smartplaylist>

And when I display it going to Videos, Playlists, it displays correctly, showing both single movies and sets.  However, if I use that playlist as the content for a widget, then only the individual movies are shown, and no grouping by sets is done.  The content tag for the panel that is the widget is this:

<content sortby="year" sortorder="ascending" limit="$NUMBER[100]" target="videos">special://profile/playlists/video/Test2021.xsp</content>

Is there a "group" tag that can be added to the content? Is there another way to accomplish this?

Any help will be much appreciated.

Regards,

Bart