It’d be great to recommend a book to a friend through the app/website and add a personal note to them where you can include why you’re recommending. If it could show up in your notifications when you have friend notifications and then have the ability to add to your To Be Read pile directly from the message. I know this might be a stretch but if it was added to your TBR to automatically include a tag of “friend-recommendation” (or something) so you can easily find those that were recommended.