Is there a way to configure an ASA Active/Standby pair to automatically transition back if the secondary is active and the primary comes back online?
I have a pair that will not transition from the secondary when the primary comes back online. I have to open a session with the primary and force the failover back manually.
Unfortunately no there isn't. If you run the firewalls in active/active mode you can achieve what you want by using failover groups but these are not available in active/standby.
So you either do it manually as you are or you could conceivably write a script in TCL or Perl that logged onto the firewalls every x number of minutes and if the standby was active and the primary had come back up and was in standby mode the script could force the failover.