Yeah. As I saw it... whenever you decide to do/change highlights, each player chooses a character other than their own, and highlights one of that character's HXs, other than that character's hx with their own character.
And whenever you roll dice based on a highlighted hx stat, you mark experience. Whether it's helping/interfering, the optional battle move of "follow through on somebody else's move", using one of those replacement moves that lets you roll hx instead of whatever, or so forth.