I have a little problem with converting some Openbook documents that includes many html-Files with a lot of internal links between the files. I import each Openbook as zip-file in Calibre. The files are sorted by name and this is as well the reading order. (Picture 1)
I recognize after converting the files into EPUB that the order of the single html files change to a wrong reading order. I open this file in Sigil to show what happens. (Picture 2)
Is it possible to integrate something like a switch into the Zip to EPUB conversion dialog where I can tell Calibre to interpret the reading order by filenames sort order? Or is there somewhere else a setup to handle this within Calibre, perhaps like a tweak?
Changing the filenames isn’t an option because of the huge amount on internal links. I can do the job with Sigil but I like to do it in Calibre too

and it's only this sorting issue what is preventing me to do it that way.