Originally Posted by chunderbunny DND Beyond will list (for free, you don't even need an account) every official monster, spell and magic item and what book they are in. You don't get page numbers though. Well crap. That makes my magic item list mostly worthless. Oh well.
A Cross-Source Index • The Bonus Guide (A Mini-Guide to Bonus Actions) • Master of Reactions — A Mini-Guide • Monster Manual Entry Reviews, Collected