50 amp service for an RV is actually 2 hot leads of 120v 50 amps each, 180º out of phase. Both Hots tie into the one neutral line. The 180º out of phase never allows 240v to be 'seen' by the neutral wire. This is actually 100 amps of power available to the RV in two separate 'legs' of 50 amps each. 120v X 100 amps =12,000 watts.
In a 30 amp RV, one hot and one neutral for up to 30 amps. 120v X 30 amps = 3,600 watts, or a little more than 1/3 the capacity of 100 amp service.
In your RV, the generator has two circuits, one tied into the transfer switch and provides power all the RV except the 2nd A/C. The second A/C is wired directly to the other circuit of the generator. Shore power can only provide power to the 30 amp service through the transfer switch.
You could replace your 30 amp shore cord with a 50 amp cord, only wiring one side to the transfer switch. The other side of the 50 amp cord could be wired to a female 30 amp outlet in the electrical bay. The wiring from the generator that goes to the 2nd A/C could be terminated with a second 30 amp female outlet in the electrical bay. Using the end of the ond 30 amp shore cord wired to the A/C unit, if you plug it in to the shore outlet, it gets powered by the 50 amp shore cord. Plugged in the other outlet, the generator would provide the power as it does now.
No new transfer switch needed, very simple solution to your wiring problem. The present 30 amp master breaker in your breaker panel limits you to 30 amps, even though the pedestal could provide up to 50 amps. The second circuit provides more than enough power to the A/C unit.
You may wish to install a circuit breaker in the circuit to protect the A/C unit since it wouldn't be protected except by the 50 amp breaker in the pedestal.