To track a dimmer, it has to have a subscription (so that it reports level). That can either be a trigger event, or a condition of a rule. The one thing it can’t be is a condition of a triggered rule, because those conditions are just tested, not subscribed to.
If it’s a condition of a rule, that condition may or may not be part of the rule, up to you and your use case. In any event, assuming it’s subscribed to, then the action for the other dimmers is “track event dimmer” on. What happens is that when the tracked dimmer (or dimmers) change level, that causes a rule evaluation, and the actions will look at the tracked dimmer’s level.
Hopefully, this will move you closer to understanding how to set it up. If not, ask more…
The “you are not authorized” is an Android mobile app bug. Usually you can just ignore it, and keep plugging along.