Title and image describes it all, can you use one mosfet to switch two things with different voltages from one microcontroller pin?
It depends on what's connected to
J12. Without knowing the details, I would say you'll likely have problems with J5 in this configuration when the FET is OFF.
Think about voltages with the FET off:
J5, pin 1 would be +5V and
J5, pin 2 would be ~12V (through
J12), and you'd have a -7V reverse voltage on the connected
J5 device. If the
J5 device can tolerate a large reverse voltage, it might work, but not recommended at first glance.
Consider adding another FET controlled by the same GPIO line instead...