Can I force external microphone detection after mic is plugged in
I've been struggling with the same issue as you and I've come up with two solutions.


Dedicated headset that stays connected to the system (not really an option for you).
Connecting my headset and briefly putting the system to sleep via the Apple menu. I literally wait for the screen of my Thunderbolt display to turn off and immediately wake it back up. If you require a password to wake the system and have it set to immediate, changing it to 5 seconds allows you to immediately sleep/wake the system without having the reenter your password.


That's the best I've come up with so far. For what it's worth I think the issue we're seeing is how headphone jacks work at an electrical level and how the system itself handles enabling and disabling the port when a cable is detected. My understanding is that headphones work on a closed loop system so when we disconnect the mic from the extension we're breaking that loop and the only way to fix it is by having the port disabled and reenabled (and only the system can do that when it detects there's no cable inserted).