You are looking for an authorial tool that is also doubles as a full-feature epub editor. Such a beast doesn't really exist (and shouldn't, in my opinion).
One should use authorial tools to write books, and use import/export tools to create epubs from those books that can then be edited/tweaked (if necessary) with Epub editor software.
I'm one of the maintainers of Sigil, and I would never recommend it as an authorial tool.
Last edited by DiapDealer; 03-02-2020 at 05:43 PM.
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