[paulrw]

Really 2 requests, both associated with formats. It would be really nice if Calibre checked to see if deleting a format from a title would leave it with no formats, and issued a warning (when I have reformatted a number of books and get distracted before I delete the redundant formats, it is really easy to delete ones not yet converted and lose the original!)
My main request though is for a bit of colour - I would like to create empty books (i.e. no associated formats) for books I have in hard copy, and for missing books in series that I want to look out for, but I need to be able to quickly distinguish which of the 3 categories a title is in. I know I can create the empty entries, and I know I could create a custom column to identify the category, but I also know that on a quick glance I would mistake paper for missing, or forget to check at all, unless it is immediately obvious by for instance the title being shown in a different colour. Accepting that this would be a major change, a good substitute would be the ability to show a coloured icon in a custom column (e.g. a green tick for "in hard copy" or a red cross for "missing altogether")