@Jellby
Thanks for telling your motives.
Until now I like Sigil (But I'm a newbie in epub at all and working at it since a week
I miss some control about the code generation.
E.g. the pattern of the IDs:
It's id="FILENAME.FILEXTENSION"
instead of just
id="FILENAME"
Or the UUID:
It is automatically added even if there's an ISBN in the metadata.
Or the pattern of the ISBN:
I'm looking for an automatical transformation from an (unformated) ISBN10 into a formated ISBN13