SEQUENCE Vertical templates

A couple months ago I experiemented with 'dropping a sequence template' onto an existing sequence  // by dropping a template - - the template options I had literally showed how the video would look based on what type of social media etc I would export to - meaning it also showed how it would look on a phone etc - - I've been looking /can't remember how I did it - or where it was from but do remember it was within premiere somehow. I'm assuming if it isn't in premiere - I installed something / tried it once, forgot how I did it - - I know - - shame - lol