So according to the newest episode of The Leafs (https://www.youtube.com/watch?v=st2S4ZKluDc @ 9:10), St. Louis offered the Leafs their 21st, 33rd, and 52nd picks for the Leafs 5th overall pick right before they nabbed Nylander. A 1st and two 2nds.
It didn't seem like the Leafs gave it much thought, probably rightfully so. Although in hindsight when you look at who St. Louis got with those picks, particularly Fabbri and Barbashev, it might not have been so bad as both those guys were projected mid-1st round picks. Still, the Leafs would have had no way of knowing those guys would have been available there, and there's no guarantee they would have picked them anyway, so good non-trade for me.