Does two-way syncing for lists exist?

[mdarbyo]

Is it possible to attach lists to other boards? Or have the same list appear on multiple boards and stay in sync on every board on which they appear?

[Jireh]

Hi, card and list syncing is not a native feature in Trello. However, there are many great third-party applications that developers make for Trello for additional functionality! 

For example, there is a Power-Up called Unito which can sync cards across different boards: https://trello.com/power-ups/5c75708a72eecc4565ecacf5/card-mirroring-with-unito

However, I'm sure there are other tools out there as well, such as Chrome extensions. I would encourage you to seek out solutions that work for your use case.