For InstanceLabel "Christina" would have a button which wuld find me all card with that label
If it is just one board then you can create a filter https://support.atlassian.com/trello/docs/filtering-for-cards-on-a-board/
If you need something to search for cards across all your boards, then you could create a dashcard https://www.atlassian.com/blog/trello/dashcards-powerup
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