Hidden (?) function in JJazzLab

Well. I just found it. Hidden arranger function under "arranger keyboard mode" which is obviously hidden by default. Now I can demonstrate what diatonic chords are :-) In Bb as it is showing correctly...
Edit: I just noticed. I was playing F7 and it took it for Adim which is obviously bullshit. Most probably I played "F" note a milisecond too late and yes - F7 is actually a Adim triad played over F. But it played F# in bassline so it could not sound good. But it works most of the time.