Old ECU potential programming for non-failsafe selectable 3 pos switch location.

Here's what I've come up with so far and will get you started for your particular situation.

ex. Kingcat w/Crow braking capability

dilemma Crow braking and brakes consume Aux 1,2,3 (all available 3 pos switches/sliders that are failsafe selectable)

how do I incorporate Aux 4/5 (only remaining 3 pos switch)

keep the smooth stop on Aux 3 (rt slider) but activate it with the snap roll button. (re: Jeteyez post)
mix Aux 3 - Aux 3 Pos 0 -20% (top) -20% (bottom) Pos 1 +100% (top) +100% (bottom)activate via Snap Roll button

your brakes still function via the slider but once the engine is in the run position, you have to utilize the snap roll button to activate your brakes otherwise you run the risk of inadvertently shutting down the engine.

keep the 3 pos switch on Aux 4/5 (deactivate the rotary knob via function 17 on JR radio)
mix Aux 3 - Aux 4/5 Pos 0 +150% (top) +150% (bottom) move the slider up and down to change number selections. listen for the low rate beeping tones and adjust %'s accordingly.

the above programming will require you to give up proportional brakes and may be awkward for thumb and forefinger guys. I guess you'll have to reach up with your left middle finger to activate your snap roll switch. In addition, smoke will have to be moved to Aux 5 (for example) and will likely have to be activated with the mix switch or some other Pmix derivative.

good luck

Buck