Why are some menu options in Crusader Kings 3 italicized?

Solution 1:

Menu sub-items are italicized if they are newly added since the last time you opened the the outliner.

Presumably, this is because if "You can declare Wars -- 2" changes to "You can declare Wars -- 3", it's pretty hard for humans to instantly recognized what was added. In this case, look for the italics.

Closing and then opening the tab and/or outliner should remove the italics.