Asana’s file picker for Box is nearly useless, from a practical standpoint. It always takes the user to the very top folder in Box, so to attach a file, one must dig down however many folder levels deep to find one’s file. If there was just a way to view / sort by “recently modified” files, that would help find 95%+ of files that would be attached. Simple filename search would be helpful too.
Without these features, I will always copy the Box.com shared file URL and paste into Asana task description or comment.