Forced epub convert
Thanks for the tip. It seemed to me that the forced conversion (calibre won't transfer the comics to the device unless I say Yes to auto-convert prompt) can be called a bug.
At least there should be an indication there on how to accept more formats to be directly transfered.
Device-compatible file extensions are known so I shouldn't need to check them, unless there is some issue I am not aware of? I understand that the plugin might have been designed for various nook devices that don't have the same file compatibility list.