You already did the next step I was going to suggest, which is figuring out the position values you want to switch the servo between. That’s great!
Since you are planning on adding more buttons and servos later, you can start by copying the “Using multiple buttons or switches to control servos” example from the “Example Scripts” section of the Maestro user’s guide. Since it uses different channel numbers (and multiple buttons) you can make the following modifications to make it work for your setup:
button_a if sequence_a endif
# button_b if sequence_b endif #comment out lines 6 and 7 by putting a `#` in front of them
# button_c if sequence_c endif
1 get_position 500 less_than #change the 0 to a 1 in the button_a subroutine (line 18)
4000 0 servo 1000 delay #change the 3 to a 0 in the sequence_a subroutine (lines 33 and 34)
6000 0 servo 500 delay
Additionally, you can change the 4000 and 6000 in sequence_a (lines 33 and 34) to your servo positions. However, note that the script uses units of quarter-microseconds, so you need to multiply your values by 4 (which should be 3968 and 5340 for 992 and 1335, respectively).
If you got that far without errors, you should be able to run the script and press the button to make the servo go to the first position for 1 second, then move to the other position. This isn’t quite what you wanted, so next, we can make the script check what position the servo is in and moves it to the other, instead.