Hi
I have no experience with the "Ju52" .... But i can awnser BASIC.
1. Trim Value.
Check the Preset itself.... Mostly they have a UNIT Flag.... Make some testings here.
E.g. show Percent, Number, degrees or so....
https://docs.flightsimulator.com/html/index.htm#t=Programming_Tools%2FSimVars%2FSimulation_Variable_Units.htm
Normaly in FS2020 we no longer need to make own recalculations in the most cases.
E.g. in the past the Altitude was in Meters*65535 ..... So we need a calc to bring them in clear feets.
Today in FS2020 we can simply change the UNIT of the Variable from e.g. "m" to "ft" and all is working !
So check if Trim Value just got a bad UNIT.
2. FLOAT on Displays....
Mobiflight "truncate" every Float behind the Transform Line ( Whatever in use or not).
So a Value of 1,99999 is technical "1" .....
If you "need" the Value behind the decimal ON YOUR DISPLAY ..... You use a simple trick,
You "multiply" it.
e.g. a Value of 1,23 must be multiply by 100 ( $*100 in transform line) to get 123 instead.
The "Decimal" itself is finaly just optical.
On 7Seg you show in that example 123 and you kust enable the decimal point right of the first diggit.
On your LCD you say "ELEV-TRIM $
,$$" .... So it technical show 123 BUT the "," is hardcoded text now!
3. YES ... Via Precondition.
You need a Indicator, what "Mode" is currently active. May there exist a Variable in the Sim in case the system is also there. If not you need a MF Variable and build this by hand.
Logic:
You build one Config, that read the Indicator .... And you build 2 Configs for the Encoder. One for Trim, one for Flaps.
Without precondition the Encoder would now controll both things same time.
With Precon you can say e.g. ..... Config for Encoder Trim only work if Indicator Config currently show "trim" e.g. 1.
Same work for Displays. You can say "Aslong Indicator = 1 show e.g. Trim Value ..... If Indicator = 2 show instead Flaps Position on the same Display".
With PReconditions and Placeholder you can do nearly everything !