Board Game Arena

Apologies if there is a better space to ask this, but I'm worried this is more user error than a bug...

Playing solo, I've unlocked a number of new mutations as I've progressed through the decks. Unfortunately, I seem stuck with "Assign one Tactics scroll" at the beginning of my runs despite having unlocked better options. Is there not a way to trade this out? I've tried clicking all over the dame place looking for an option, but nothing presents clearly. Any help appreciated!

At the start of the run, there's an option to Modify Mutation Board. After you click that, click the card you want to remove from the board, then at the top pick a different card to take it's place. If this is already what you're doing and it doesn't work, then it might be a bug.