1. May be it is a dumb question: What is the difference between the second and third tabs for add/save in preferences. Saving books vs. sending to Device? It appears that for saving the books in Calibre library, Adding books tab is only effective.
2. I use
(?P<title>.+)-(?P<author>[^_].+)-(?P<series>[^_].+)-(?P<series index >[^_].+)
in the adding books and
{author_sort}/{series}/{authors} - {title} - {series} - {series_index}
in the saving books (and in sending to device tab also); but the series index does not show up. I must be doing something wrong in the regex strings!
3. Is it possible to automatically skip the missing item in the file name. I am using the - x - for the missing string like {series}.
Thanks for the answer.