As you've discovered, Qlik Sense only recognizes 3 fields in a KML file: Name, Point, and Area. This post helped me: Re: Qlik Sense Mapping and County KML.
You could create a separate spreadsheet with just Name and Region and include that file in your load script. Qlik Sense will automatically link the "Name" field in both files which should give you access to the Region in your map.
I hope this helps.