If an activity needs to be performed at a certain station, you can lock the activity to the station before running a default balance. This ensures the activity will not be moved to another station during a rebalance. To lock an activity to a station, right-click on the activity and select a lock to station.
As you can see the check there is a check mark in the fixed column indicating that the activity is locked to the station. to unlock the activity right-click again, and select unlock from station.