>>Nur ging es hier ja um die passende Übersetzung des - auf einem englischen Notenblatt stehenden - Wortes "dolce".
That's the only side that the discussion has considered so far. But before deleting the German terms, it seems to me that you should consider whether the entries would be useful to English speakers who encounter the German terms in a score. Only Anne has touched on that so far, in #18.
I'm not sure, for example, that schmelzend is necessarily exactly like dolce, but if this entry wasn't there, schmelzend might not even appear in the dictionary, since -end is a regular participle ending. And for someone who's just learning a piano piece and doesn't otherwise speak German, 'dolce' might be a useful additional translation option, since 'meltingly' wouldn't necessarily be very clear -- is that like emotional or romantic, in the sense of 'She gave him a melting glance'; or is it more like fluid, flowing; or is it somehow blurred, with a lot of pedal, one note melting into the next?
Sanft is maybe also tricky in the context of music, because literally it looks like it's a cognate with 'soft,' but 'softly' would mean quietly, piano, whereas 'sanft' probably means something more like gently, which isn't quite the same.
And as for süß and lieblich, if there's a difference between them, I'm not sure I could explain it. But translating them as 'sweet(ly)' vs. 'dolce' might be a different nuance, since 'sweet' in English can lean more toward sentimental, cloying, saccharine, whereas 'dolce' doesn't have any of those negative connotations of 'too sweet.'
To my ears at least. In any case, I wonder if it might not still be worth hearing from a few other people familiar with musical terms in both languages, thinking about not only E>D but also D>E.