I’m not sure if it’s expected/intended, Okoye’s Wakanda Forever does not add bonus damage to Mockingbird’s Secret Mission bonus damage.
For comparison, 2* Black Widow’s Espionage receives a bonus from Wakanda Forever.
Espionage is actually a separate damage source triggered by the match, while Secret Mission merely increases the damage done by the match. That’s why Wakanda Forever works on the one, but not the other.