NOTATIO

May I ask you a comment on this?

I have slurs crashing with alterations. I tried moving up the slur, or deforming it to bypass the alteration, but at last here is what I came to. What do you think? I only rarely have seen this solution in printed music.

On a side, I have some similar problems with the appoggiaturas slurs. What do you recommend? This is the program's default.

I have no problem with slurs crossing through the stem of the flat. In fact, I find the "whiteout" style in the top two examples more visually distracting. I think it's because the slur is relatively short that it kind of looks like a pair of articulations rather than a broken slur. Others may have a different opinion than me.

Here's a potential solution for all your questions. See what you think:

I agree: a slur crossing the stem of the flat is absolutely fine. Slurs on appoggiature could do with a bit of adjustment: either manually or the settings.

Which app is this?

Thanks very much all.
It's Sibelius with November font.
Sibelius uses the same overall settings for both the slurs on appoggiaturas and on normal-sized noteheads. I seem to see the example by tisimst has thinner slurs when on appoggiaturas, am I wrong? Or maybe thay are only longer and so they seem thinner as well. I'll play manually with that. By the way, they are all excellent solutions, I'll try to imitate them
I was under the wrong believing the slur crossing the is forbidden, so I ruled out. I do prefer the crossing to the white-out, as suggested.

Some engravers prefer not to run slurs through accidentals when possible. I only do it reluctantly and usually try to only touch the end of the accidental. It is avoided by raising the slur higher (or lower) so that the end points of the slur are farther from the note heads, no crime. I see this strategy in some of the examples from Gould's Behind Bars although she doesn't actually seem to discuss the issue, or at least I couldn't find a discussion.

I agree.
Cutting the stem of the flat is fine, the rest—if possible—is to be avoided.
If nothing works (and it happens a lot when the slur is short, e.g. two notes, and the interval is very big) then move the endpoints away from the noteheads.

But sometimes the alternatives are worse and one must grin and bear it. Here is a case with naturals:

Yep, as long as it’s still absolutely clear what the accidental is and what the symbol crossing through it is, I have no problem with the occasional crossing.

It looks totally fine to my eyes. As tisimst pointed out: as long as it is clear.