Ability to control defaults in transposition menu.

FWIW, instead of just controlling defaults, I think better still would be able to define named presets - or perhaps to simply add some predefined ones. I assume the reason you use the transpose dialog much is to produce lead sheets for transposing instruments. It seems it would be nice if there was a preset to produce appropriate Bb & Eb transpositions, for example.

Mmm.. presets... not sure I like this.
First, we could persist the settings between sessions.
Second, for Eb/Bb transposition, we already have a solution no? User write the leadsheet in C, change instrument to Bb trumpet and transposition is done. The same for Eb instrument. Am I wrong? I'm not sure mixing the transpose dialog with transposing instruments will make MuseScore easier to use and understand...

It is true that changing instrument would do the job. For whatever reason I don't think most of us do it that way, but there probably isn't a reason we couldn't. Except for #62341: Chord symbols don't transpose when changing instrument/transposition in staff properties - this needs to be fixed (PR already pending) in order for that to be viable.

Simply remembering last settings is fine by me, I don't use that dialog often apenough to really care much anyhow.

"For whatever reason I don't think most of us do it that way."

Really? I do.

For those who are not changing instrument to go from a C leadsheet to a Bb leadsheet. How are you doing it? If I understand correctly, using the current transposition dialog changes the sounding pitches and the position of the notes and so it's not the right thing to do, correct? You are compensating in the Staff properties? Or you don't care about playback?

I can see how we could add a "Quick transposition" panel featuring C-> Bb, Bb->C and so on... in the transposition dialog, or we could append these to the interval list items or the Keys list item but still the sound would be wrong. Do I miss something?

I'd simply change Instrument to a Bb one, like clarinet

I created a template specifically to do this (see attached). The only downside is having to copy the leadsheet in the score several times (although the "Ghost staves" feature I requested would remedy that ;) Once the leadsheet is entered and copied, all that's needed is print the required parts.

lasconic: I normally use the transpose dialog to transpose up a major second (Bb) or major sixth (Eb) if the piece does not use key signatures (many of mine do not). If the piece does use key signatures, I usually just figure out the new signature and transpose that way.

Either way, this does indeed change playback, but I don't care about playback for leadsheets. You're right, though, it *does* make more sense to change instrument rather than than use the transpose dialog for that reason. So maybe I'll get in that habit some day. Or maybe I'll start using a template like the one Xasman posted. More likely, I'd consider trying something simpler: making my lead sheet template use a Bb transposition but start in concert pitch mode. So I get a Bb transposition with a single click.

Realistically, when transposing lead sheets, I spend way more time going through and rethinking enharmonic spellings - for both notes and chord symbols - than I do actually interacting with the dialog. I choose my spellings taking into consideration what is musically correct but also what I think will be most readable given the context, and I would never expect an algorithm to get "right", so I have no illusions about trying to automate this. And of course, I only transpose twice per chart (once for Bb, once for Eb), so the time spent transposing is pretty insignificant compared to the total time I spend on the chart.

So the bottom line is, for me, if a simple change improves the situation for some people, great, but it's probably not worth coming up with anything too grandiose.