TL;DRBlueprint sharing in multiplayer was effectively killed after the .37 update. Currently you need to use game blueprints (No one is going to dump their entire library in game BPs) or manually make a copy of a blueprint and share it in chat.
What ?With the recent blueprint updates, in multi player we are no longer able to view other players blueprint libraries. Sharing BP's is a critical part of the multiplayer experience. Of course the game blueprints still exist, but with the updates unless everyone knows what they're doing, players can unintentionally remove blueprints from the library (unless you specifically know to click the copy button, selecting a blueprint from game blueprints removes it for everyone.) And of course, the game blueprint library only shows what has been shared and hasn't been deleted.
Essentially, I am suggesting that you implement the ability to browse and copy other players blueprints in multiplayer. There are third party websites for this, but they are far from an ideal way to share, especially for newer players.