[KevinH]

Jon is correct. And again requests for new features should be labelled as such and should include how this feature request might benefit others.

It sounds like you just want to use Sigil to "fix" a pet peeve in your current ebook library as quickly and easily as possible and want Sigil to be adapted for your use. You even ruled out plugins for some reason.

To be frank, a "feature" request like this is never going to be accepted by me. There is just no general need for such a "feature".

My suggestion is to get a real epub3 reader that interprets linear="no" the way you want it to.