Instead of opening a new project for every different ebook (KPUB2 or EPUB) Kotobee Author allows you to import EPUB files into your current project. This will allow you to append any EPUB extension ebook to your already open ebook be it a new one or old.

This is done simply by clicking the Import EPUB button in the edit window above the book title.

You will then be met with the import EPUB window which will prompt you to browse for the EPUB file. Note if you want to import a KPUB2 file simply rename it and change the extension from .kpub2 to .epub.

By selecting the file with your file explorer it will be selected ready for importing. 

The options are:

Entire book This will take the EPUB book as a whole and add it with its current format.
Single chapter After an EPUB file is selected the single chapter option will be available. This allows the user to select one of the chapters of the selected book to be added to the current project.
Replace with current chapter This option will use the selected single chapter to overwrite the current chapter open in your ebook.

After selecting which option you prefer click on the Import button will import the EPUB file entirely or the selected chapter. This will be added to your currently open project; appending it or replacing the chapter if selected.