Hi @laurajane ,
We published a detailed walkthrough in the community that directly addresses this challenge. It shows you how to trigger mirror automations based on all mirror statuses of low level boards being something. So you can set the status on a high level board based when all mirror statuses are “Done”.
You might find it really helpful: https://community.monday.com/t/how-to-trigger-a-status-change-based-on-a-percentage-of-completed-mirror-statuses/120422
Here’s a video showing it in action, in the video we illustrate it working with a Text column but you can set any column type as the destination:
Hope this helps you out!