Just came back to say again: Thanks for the great plugin. I use it a lot.
With it, I was able to create:
1) 'Clean-up' chain that:
- Create a folder structure;
- Remove unwanted files, embedded calibre metadata, Sigil and KindleUnpack artifacts;
- Fix all HTMLs;
- Use full page SVGs for covers;
- Convert NAV landmarks and OPF guide to pt-BR;
- Remove 'lang' and 'xml:lang' from <body> tag;
- Fix missing 'alt' attribute on <img> tags;
- Remove 'linear="no"' from OPF;
- Customizable 'Pretty print all files' (adpted from calibre code, to avoid certain things, like adding spaces between the lines);
- Run 'Check Book' at the end
2) Merge splited files automatically (thanks for the chain!)
3) Run 'Check Book' and fix all errors automatically
4) Replace invalids IDs
5) A customizable 'Upgrade to EPUB3' based on calibre orginal tool, that can keep the NCX and the <guide> element (in the OPF). This gives me maximum backward compatibility
I can't thank you enough for this plugin. Made my life a lot easier. =)