Any OneNote add-ins worth trying for campaign notes?

I’d start with the task that’s actually slowing you down, rather than browsing add-ins at random. For example, is it awkward to prep sessions, find recurring details, or share player-facing information? Look for an add-in only if it clearly helps with one of those jobs.

Before relying on one, check that it works with your OneNote version and setup, and try it on a copy of your notes. If it asks for access to campaign material, check what it can see and whether that fits your group.

No particular add-in stands out from the information here, so I wouldn’t want to name one as a sure bet. For GM notes, a simple structure you can search and reuse may be more helpful than adding another tool. If you have a specific repetitive task in mind, that would make it easier to judge what’s worth trying.