Would be great to have more mirror column functionality.
For example,
If an item is created in a certain board with mirror columns, maybe make some functionality where an automation (i.e. triggered by item creation) from that board can change the status of the mirror column in the other board, or any column in the other board for that matter.
Also allow mass changing of mirror columns (selecting mass items and trying to change mirror columns only changes one at a time instead of all items that are selected).