Let me get this straight:

If I understand you correctly, in the score all the C instruments display a key signature of 8 flats (= F♭ major, double flat for the B scale step) - right?

But in the score the B♭ Clarinet staff displays a key signature of 5 flats, not 6 flats - right?

There must be something wrong in the Finale document.

When the Concert Key displays 8 flats, the B♭ Clarinet should display 6 flats.

In this situation you would normally set the Concert Key to E major (= 4 sharps), rather than F♭ major (= 8 flats).

* Have you tried E major?

* If you have tried E major, what key signature does the B♭ Clarinet staff display when the Concert Key is set to E major?

Correct.

My Finale version does not "go" beyond the "seventh" Flat, Concert Pitch.

I would require the Concert Pitch of eight (8) Flats. (Bb Clarinet = 6 Flats)

Using Concert E Major (4 Sharps) displays Bb Clarinet 6 Sharps.

Using Concert B Major (5 Sharps) displays Bb Clarinet 5 Flats.

Using Concert F# Major (6 Sharps) displays Bb Clarinet 4 Flats.

I guess I will convert it mentally/by hand.   ;-(

Clyde

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No need to convert “mentally/by hand”.

… require the Concert Pitch of eight (8) Flats. (Bb Clarinet = 6 Flats) …

Finale can display a Concert Key of 8 Flats.

From your latest post it looks like the problem not the Clarinet’s B♭ transposition, but rather getting a display of {8 Flats} in the C instruments.

You tell that you can not make the Concert Key go beyond {7 Flats} - right?

I do not understand why you would notate the C instruments in 8 Flats (rather than in 4 Sharps).

Please explain; what is the problem you are trying to solve?

However, Finale can do it:

In the dialog box Key Signature, in the pop up menu at the top, choose Nonstandard…

In the dialog box Nonstandard Key Signature, click the button {Next} twice, to get to Linear Key Format 2.

The first two Linear Keys Formats (= 0 and 1) are “hardwired”, hence you need Linear Key Format 2.

You can set the Number of Accidentals to -8 when you are in Linear Key Format 2.

Thank You, Peter!  Done.

Works well with the Key Signature drop-down menu.

Thank You for the Directions.

Clyde

There's a place in this score where the C instruments are in 4 sharps (F in 5 sharps), but the Bbs and Ebs are in 6 and 5 flats respectively.  If the score is in sharps but you want the clarinet to be in flats, in Finale, another way you can do this is with a temporary "instrument change" to a clarinet in "A#" which transposes a diminished 3rd instead of the usual M2. 

The passage is below.