>>> The notes d♯ to e♭ have different pitches in the staff notation >>> system, which cannot express E12 enharmonic equivalents, so this >>> is slur. So it should be a slur that looks like slur.
I disagree. For all practical purposes in standard classical music, enharmonic equivalents *do* sound the same. What you are referring to IMHO is a special case that might be controlled by a flag. > I can think of special cases: Perhaps the tie and the slur are > rendered slightly differently, say of different thickness, so in > Werner's example it should be a tie in style. Somebody might want > to indicate an E12 enharmonic equivalence, as in your example, even > though it is not so in the staff notation system, and then it should > be a tie in style. As mentioned above: This might be controlled by a flag. Or maybe a special “E12_tie_slur” engraver can handle this. Werner