Hey!
I just posted this so I thought I’d give you the link to read as well. If you search for “280” in the templates you can find the automation formula for " When [mirror] status changes to something change another status to something"
As for the 2nd scenario, you could use this mirrored status to show a specific status [strictly for automation purposes], the board B would see this status and trigger another automation which connects all boards A & C with B, and then change back the status to whatever it is you wish it to be showing as.
For example:
In our case we manage engineers and in-field services. In our masterboard we have multiple services but in each engineers board you have only their own services. Sometimes we want to reassign engineers, or reset the data in both boards. I set up a Status column called [AUTOMATION STATUS] which is basically keyword/commands for the Engineers board’s automations to pick up and either delete the item or duplicate or connect to other boards etc. All because of this mirrored column status as a trigger:
I hope this helps 