I have the priority card and have used the $75 travel credit (I think) and bought 2 upgraded boardings. I assume its my responsibility to keep track of these 2 perks as I cannot find anywhere on my Southwest account or my Chase account that tracks these for me.
You should be able to log in to your Chase account and select to view "all transactions". When I do that in the Chase mobile app all of my payments and credits are red while all expenses are blue. Then scroll and review all of the red transactions. My $75 travel credit is labeled "TRAVEL CREDIT $75/YEAR".