Are you sure you’re in the correct layer, when applying the slurs? Does the ossia use layers, the same as the regular score? (It’s not a tool I use.)

I believe I’ve heard of people exporting ossia measures as graphics, and then pasting them back into the score. Would that work for you?

1) For showing, how to execute various trills, it is not standard practice to add slurs in the ossia.

2) You tell that you have entered the slurs "as note shapes” in the scratch staff.

I am not sure what you mean by your words “as note shapes”.

What is a “note shape”?

In “Finale-speak” the usual meaning of “note shape” is “notehead”, as in the Note Shape Tool.

3) It is a known limitation in the Ossia Tool that ossias do not display Smart Shapes (and also neither Articulations nor Lyrics nor Chord Symbols).

Take a look at the dialog box Ossia Measure Designer, to see what items an ossia can display.

Workaround:

Instead of using the Ossia Tool, use the Staff Tool.

Add an extra staff to the document.

Use this extra staff for the ossias, and hide the extra staff where it is not needed.

You can resize the extra staff with the Resize Tool.

1)  I know.  But this is for teaching and I want the slurs to show, especially for long appoggiaturas, which is one of the lesson themes this piece is covering.

2)  My nomenclature was a tad off.  There are Smart Shapes attached to measures and those attached to notes, or beats.  Slurs are obviously attached to the latter.  I was referring to those.  This is a reference to Robert's Mass Copy where he isolates SS attached to measures and SS attached to notes.  I use his plugin set so much it pervades my thought process.

3)  That's what I was afraid of, as I referred to the Ossia Measure Designer dialog in my original message. Time for a feature request I guess.

All of the ossias were generated from a scratch staff that was hidden thruout the file.  I then used the Ossia tool to assign them to specific measures and tweak the appearance.

I just ran into exactly this problem. I also have some lyrics, and the commas are not showing up between syllables.

The workaround I am using is to create a slur on other notes on the same page, and then drag it to the ossia measure and adjust the shape. I will add the hyphens with the text tool. It's a pain in the neck, of course, but so far it seems to work.

Have you tried the graphic workaround?

Actually I find using the slur tool is a great deal quicker and easier than creating a graphic outside Finale and importing it. You just enter the slur, drag it, and adjust it. The only real issue is that, if and when you adjust the the notes the slur is actually attached to, you of course have to adjust the slur again. 

...or did you mean creating a slur in the shape creator? Take your pick. I still found creating a slur on the page faster -- probably because I am not as skilled at using that shape designer; sizing never comes out quite right. Anyway, however you create the slur, you still cant attach it to the Ossia, can you?

Well, I just read your first comment again (Mr. Rosen). I gather you mean that one can select the original measure, export it as a graphic, and then paste it in where it is wanted as an ossia. It would not work for me in this instance but it might in future. In any case, thanks for the suggestion.