Thank you everybody. I'll use the search and replace and Regex tips when I need them. Now I'm using the 'replace named entities' feature confidently. It made me find that Sigil did not support Unicode characters (at least for the equivalent, which is brought back to named entity if you save the file), whilst Amanuensis did.
I think this editing tool is really interesting and useful. But I would like to know which proportion of the innumerable Calibre users can use it: In France, I assume that one ebook user upon two uses Calibre, as a rule of thumb. But most of them totally ignore HTML (and Regex!). Thank you for those who are able to use the new feature. I like this in Calibre: it is not made 'for noobs', but it can be used by noobs with results they find satisfactory
