[KevinH]

The rules on epub structure or layout have never really been fixed under epub2 and have gotten more fluid under epub3. All versions of Sigil before 1.0 (even way back to 0.6 and 0.7.2) forced every epub into Sigil's own hard coded structure. We changed that.

For epub2, the spec used to recommend but not require a folder like OEBPS to hold the resource files but does not specify a name. It also does not require separate sub-folders by type (like Styles or styles or ...). It does not specify a name for the opf, so content.opf or package.opf or ... are allowed. Same for the ncx.

So all of that structure, Sigil forced on every epub it edited immediately when opened. This act of forcing a structure resulted in almost every file in the epub to be edited to update links, urls, and references. Neither of these are something professional book editors typically like.

For epub3, the spec is even looser so even things like the OEBPS are not required or even recommended.

So Sigil post 1.0 finally follows the spec (which is why it was named version 1.0!) so you can create any layout you want. It also provides a simple tool to convert everything back to the old "standard" locations that used to be hard-coded by Sigil since it is favoured by many and is a simple logical structure.

Hope this helps. Just understand that Book Browser is NOT a File Explorer NOR a File Browser, it uses file type groupings as logical folders to organize files by type, making it easy to find files and to multi-select files of the same type for all of Book Browser's other tools (renaming, moving, deleting, etc). You determine the actual structure you want.