Scenario:
John has a list of projects on one board. He has another board with tasks linked to the project board. On the projects board, he would like to put in a column showing the earliest due date for any remaining task. (to see which project is the most urgent). Unfortunately, when he tries to do so, he sees that the mirror column only shows the due date of the very first task, which was finished months ago. He wishes he could make the mirrored column show him the earliest due date after filtering out all closed tasks.
Solution: add an ability to filter a mirrored column to only mirror links that meet certain conditions