Case Fan MKS Gen L

I am new to this forum. So please forgive my inexperience. I would like my case fan to be attached to the location marked in yellow. It is a 12/24v spot. I am up for other locations as well. However. I would like to have the fans turn on when the stepper motors turn on, and then turn off after 120 seconds of inactivity. My new drivers get hot and I want to make sure they are well cooled. I need help with where in marlin 1.1.8 to change the firmware and how.

D9 is used by the part cooling fan
D7 is used by the hot end fan (my back up plan is to wire in parallel to this port, but that puts 3 fans on that port, and not exactly what I need)

I am running two 24v fans in parallel right now, but have two 12v fans on the way that I am going to run in series (same fan x 2).

The pins you have indicated are not software controllable

They are always on

Are there any other good pins?

To be software controlled the fan needs to be connected via a mosfet

there are only 4 mosfets on your board
fan, E0, E1 and BED, all used

So you will need to add a mosfet
This should be connected to a PWM I/O line