question

I too am noticing alt_mode_slot_index = 2 is not showing a value when set. If I use 0,1,3 all three indexes for AUTOPILOT ALTITUDE LOCK VAR return a value.

I think in most cases you should set alt_mode_slot_index = 0 since the default is index 1 and if it gets changed zero will read ALL the active indexes. So I think the only reason to set the alt_mode_slot_index = 1 or 2 or 3 is if you only want that slot be readable. I figure these options were created so there is memory for more complex altitude selectors.

When this config parameter is set to 0, the altitude capture will always use whatever the currently observed slot is set to and will not change slots or write to any slots on capture.

@FlyingRaccoon Can you confirm there is a bug and if we are not using more than 1 altitude selector should we be using zero? I suspect you only choose 1,2 if you need a specific index

Presently the GNS AP is hardcoded to look at altitude slot 1, which is due currently to a limitation of the JS instruments not being able to read what the cfg slot setting is. We hope to make this work a little less awkwardly in the future. I thought that we added this information to our developer doc but it appears it was mistakenly not included. We will log that and get that updated.

However, for now, I would use alt_mode_slot_index=1 in your CFG, and then have the non-autopilot controlling altimeters use slots 2 and 3 while having the autopilot controlling altimeter use slot 1. That being said, we only intercept AP_ALT_VAR_* events for index 1: the rest are passed through to the sim unaltered. We do not intercept the KOHLSMAN_SET/INC/DEC events anywhere so you should see those reflected in the simvars regardless of your CFG settings.