One book and many formats

Hello,

I use Calibre to convert comic books, from epub or cbz to pdf.
It works perfectly...

But, after the conversion, I have only one line in Calibre with many formats (ex: cbz, pdf).
Then, I purge Calibre library...
When I import books, I have one line by book format and not only one line by book...
Is it possible for Calibre to recognize books and show only one line by books (with the list of formats)?

Thank you.

David.