You cannot do this in tags... Mobile App tags is extremely limited functionality.. In fact, I don't set anything for the mobile app in Tags... The only thing I do with Tags is to set extensions and make sure that our developers are using the proper extension versions in the code....
Everything is either set directly by developers, or sent via context variables which are then mapped in processing rules.
With Mobile App Tags, there is no scripting available.. there is no ability to do any thing other than the most basic logic.
So in order to track products list in the app, you will actually need your developers to set all the values and pass it on your trackState or trackAction calls...
See https://developer.adobe.com/client-sdks/documentation/adobe-analytics/product-variable/
You cannot even map products with Processing Rules, Products must be set using &&products= by your developers.