In all programming, SETUP LIST, MONITOR is very useful to see what the programming is doing on the channels.
(To replicate the THRO channel on the AUX channel).
By default, the GEAR SW changes the position of CH5 and the FLAP SW changes the position on AUX (CH6). I didn't notice readily a way to disable the operation of the GEAR SW, but the FLAP SW can be disabled by ADJUST LIST, FLAPS and setting all fields to 0.
Next, set THRO -> FLAP ACT, RATE D -100% U -100%. I had SW ON TRIM INH though no idea what those settings do. Perhaps SW chooses the switch that enables this mix and ON means "always on"?