You can update and overwrite your Library Items straight from your itinerary!
Note: This will overwrite all of the information on the Library Event with what you have on the itinerary version of the event, including ideas, notes, and photos. And please note, this applies only to Library Events, not Places.
Here's how!
1. Go to the Event
Go to the Event in the itinerary you'd like to save.
2. Edit the Event
Click on the pencil icon that appears in the top right corner of the Event when you hover your mouse on the Event.
2. Click the More(...) button
Clicking on the button with the ellipsis next to Done Editing. This will bring up a few options:
Duplicate
Save to Library
Delete
3. Click on Save to Library
4. Click Overwrite Library Event
You'll be presented with the option to add a label/more labels to help organize your library, but you don't have to!