To bad, really sad. This feature would really help our work iso sub-subitems..
People have been asking for this since the Corona era (2020).
Here is demo of an app I have built to solve this problem. Please let me know if this will solve your use-case.
Hi Community! We appreciate your understanding as our Product team continues to explore the best way to bring this feature to life for you all. This feature still remains on our long-term roadmap.
Thank you for sharing your use cases with us–our team understands the importance of this feature to expedite and streamline how data is being synced from connected boards. We are looking into different ways of optimizing the Mirror Column settings to develop this capability, but we do not yet have an exact timeline for development. We will continue to update you all here as we make progress!
Hello everyone,
We have developed a solution for this:
Currently, it’s in review to be added to the marketplace.
Here is a demo of how it works:
You can install the app using this link.
You could try the Mirror Item Multiple Boards app. We solve a bunch of these use-cases 
Reach out to us at support@fortimus.co or schedule a call here.