Flip-switch to change trims or flight mode during DLG-start by moving the elvator-stick over a defined position,
reset by unused trim-knob

How it works:

on the mixer:
select an unused virtual channel, rename it for better understanding (e.g.: TRM-SW)
set the type to 'complex'
set the source to 'TRM-SW'
set the Curve to '1to1'
set the scale to '0'
set the trim button to 'Trim'
SAVE

Next: 
on the trim page:
select the unused TRIM (THR)
set the INPUT to an unused virtual channel (TRM-SW)
set the step to 'Momentary'
set the Trim+ to the trim in question
set the Trim- to None
SAVE

Now the Flip-switch:
on the mixer:
select an unused virtual channel, rename it for better understanding (e.g.: FH1, flip helper 1)
set the type to 'complex'
set the Source to 'elevator'
set the Curve to 'MIN/MAX'
Enter 'MIN/MAX'
set the switch value to desired (e.g. '50'), SAVE
set the scale to '100'
set the trim button to 'NO Trim'
SAVE

now do the same same with a second virtual channel:
select an unused virtual channel, rename it for better understanding (e.g.: FH2, flip helper 2)
set the type to 'complex'
set the Source to 'elevator'
set the Curve to 'MIN/MAX'
Enter 'MIN/MAX'
set the switch value to desired (e.g. '50'), SAVE
set the scale to '100'
set the trim button to 'NO Trim'
SAVE

now the FLIP:
select an unused virtual channel, rename it for better understanding (e.g.: FLIP)
set the type to 'complex'
set Mixers to '2'
goto page 1
set the Switch 'FH1'
set MUX to 'replace'
set the Source to 'FH2'
set the Curve to '1to1'
set the scale to '100'
set the trim button to 'NO Trim'
SAVE
goto page 2
set the Switch 'TRM-SW'
set MUX to 'replace'
set the Source to 'FH1'
set the Curve to '1to1'
set the scale to '100'
set the trim button to 'NO Trim'
SAVE

That's it. Now you can use the FLIP channel as a switch for whatever, reset by unused trim knob.