I would like to know if there is a way to export a list and include automaticly Item IDs of the books. I want to use the list for my database and entering manualy Custom IDS for each book would take a long time. I wish there was an option to add IDs from the dropdown column.
You can use the "Collection ID" field. You can activate it in Preferences -> Fields. Select all your books and use the "Book -> Incremental Collection ID..." command. From here you can fill the fields with "Apply To Selection" and also set the checkbox so new added books get the next ID automatically.
There is an internal ID you can use as well, but it's never displayed in the program. So you would need to create a text export template (they go in ~/Library/Application Support/Bookpedia/Templates) and use:
<!-BeginRepeat-->[key:title] = [key:uid]
<!-EndRepeat-->
This is not as convenient as you would not be able to cross check it easily in Bookpedia UI, but if you only care about the printed/exported listing then this would be fine.
I am pretty sure they are custom fields renamed with hyphens. It's a smart way to keep them together and obvious that they are custom fields. Especially important here as some have the same name as existing fields.