On the USM you could configure the prop channel #2 to activate any function even that channel was used for the steering servo but it seems this option is blocked on the SFR once "Steering with prop. channel #2" is activated.
If you do not use the SFR to control steering inertia, limit the steering angle, use "Bending light via steering (Prop. channel #2)" or transmit steering signals via IR you can use the same work-around:
Unselect "Steering with prop. channel #2" and "Automatic indicator lights while turning", then go to Proportional channels > Prop #2 and assign under "In position (static)" Multi Function 1 to area A and Multi Function 2 to area D.
Extend area A and D by using the sliders on the left (blue square) if you want the indicators to switch on earlier.
Since the steering servo is now disabled use a Y-cable from the receiver to split the signal to SFR Prop #2 and servo.