Fix Confusing Accidentals

See my response to your previous question. I understood you just fine, and my response addressed the best ways of achieving something along the lines of what you are saying but also why it isn't that simple. For example, running Notes / Respell Pitches gives you exactly what you ask for. But as a professional pianist often asked to sight-read music like this, I would suggest that while the first measure might have been improved in this case, the second was not. The prevailing harmony in the second half of the bar is probably something like A7b9. If the left hand of the accompaniment, or the lower voices of the choral arrangement, had a prominent "A", then lying about the spelling of the C# would be counterproductive.

BTW, it is also an oversimplification to say that flats are always preferred in flat keys. As the above example demonstrates, C# in the key of F is actually going to be quite common for very good harmonic reasons. A7 is V7/vi, an extremely common chord. Db would occur in the context of a iv chord, which is admittedly common too but probably not as common, and in any any case, the correct spelling absolutely depends on knowing this context. Deliberately using a spelling not consistent with the harmony is almost always a mistake and will be more likely to lead to reading errors for the accompanist. Also, there is a huge difference between rules for spelling of "essential" (to the harmony) chromaticism versus "non-essential" (eg, passing tones). In the latter case, key doesn't enter into it much at all it's about the direction of the line and which way the note resolves.

Bottom line, never depend on defaults, nor on a simplistic linear analysis to always produce the best results. If you must use MIDI to enter your pitches (not very efficient for exactly this reason) then by all means try Respell Pitches afterwards, but please do the accompanist a favor and go through again and correct spellings by hand according to actual harmonic context.

It's also worth noting that even the "simplistic linear analysis" is not so simple. For example, you suggested the algorithm be to not use the same line/space as the previous note, but that's actually the wrong answer half the time. As with much in music (and life!), it's not about where you came from but where you are going. So, C-C#-C might not be as good as C-Db-C - in this case, Db is better than C# - but C-C#-D is absolutely better than C-Db-D. That's because the optimum spelling of the middle note depends not on the previous note as much as the next. And this is why it is necessary to wait until you are done to run Respell Pitches, because at the moment you enter the C#/Db, MuseScore has no way of know what the next note will be.