I understand why Makemusic created the Score Manager. And perhaps it makes life easier for novice users. But for experienced users it is (still) a major regression after five years and counting.
It basically replaced Staff Styles for instrument changes. But let us count the ways Staff Styles remain superior:
1) You can see Staff Styles as you work. Right now the only way to discover the exact bar of an instrument change is to open the Score Manager and fish it out. Oof.
2) You can easily apply Staff Styles and (equally important) unapply them in specified bars. As far as I can tell, the only way right now to change the bars of a doubling instrument is to delete it completely and reapply it. Change Instrument does literally nothing when I select a portion of a doubling instrument and try to revert it to the main instrument. No message, no Undo entry, nothing. Really? (I would love to be told I missed something.)
3) A Staff Style can easily be applied to a single measure or even a partial measure. Change Instrument won't do it, even for a full bar. Not sure about other ways.
4) It seems like you can only have one instrument per Garritan instrument. Consider this example. I would like to have someone double on a large semi-pitched bell and on tubular bells. It turns out the best playback option in Finale for the large semi-pitched bell is also the Garritan tubular bells. I have not been able to figure out a simple way to prevent my instrument changes from always being one name (with 1-line staff) or the other name with 5-line staff. Maybe it's possible with a lot of fiddling in Score Manager. I haven't pursued it. Staff Styles to override Score Manager's stubbornness are simply far easier in this situation.
5) Applying Change Instrument to a few bars apparently removes all midmeasure clef changes throughout the entire staff.
I also have a huge related issue with Human Playback. It appears not to recognize, for example, a violin unless the base instrument name starts with the word "Violin". I have had to prepend the word "Violin" in hidden text to "I" and "II" in orchestral scores to get, e.g., pizz and arco playback. Recently I discovered that Human Playback does not recognize a violin as a doubling instrument. That is, the underlying instrument is something else, and where I used "Change Instrument" to specify violin, none of the pizz, arco stuff happens. Human playback should be based on the playback sound and not the instrument name.