There's no image in the question and I don't have a copy of Dorico, but I'm guessing that the slurs look like the ones in this question: What does a line through a tie indicate?
I can't find much official information from publishers online outlining their standard editorial practice, but looking at the editions I have, at least one publisher does use this (or did recently; possibly they no longer do) - ABRSM. My copy of the Beethoven piano sonatas (Barry Cooper edition) says in the preface matter:
Editorial ties and slurs [...] are marked thus: (a picture of a slur with a small vertical line through the middle).
Other editorial additions [...] are shown by means of small type or square brackets
and indeed, there are many examples of such editorial slurs throughout. The example in the linked question doesn't have its publisher mentioned that I can see, but other aspects of the typesetting look ABRSM-y to me.
Most of the other publishers I've checked do something else - e.g. Henle and Edition Peters seem to put theirs in brackets; Bärenreiter seem to use dotted slurs (I assume they indicate phrasing slurs some other way).
(I think there are pros and cons to both options - bracketed slurs have the benefit of being consistent with other editorial markings, which are usually bracketed; however, the slurs-with-lines-through have the benefit of not taking up any extra horizontal space compared to a non-editorial slur.)
