Crystal from Trello Support here!
While Trello doesn't support board nesting you can use a few different workarounds to achieve card/board syncing!
You can add a link from one card to another to show a preview of the board and refer back to it easily. Here's a guide on that: https://help.trello.com/article/824-sharing-links-to-cards-and-boards
You can also use these third party Power-ups to keep cards in sync:
If you had to thrive a new habit during a lockdown, what would it be? Trello
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