In this dialog you can select which books you wish to operate on, either all books, or only the New Testament, or only the current book, and so forth. Individual books can be added or removed by clicking on them.
To select one or more books choose button "No books" and then click a book and the book gets selected.
If you want to choose another book, press Ctrl and click on the book.
Shift combined with click selects, if one book is selected already, all the other books between the selected and the clicked one.
There are hotkeys for No books, Old Testament, New Testament, All books, and Current book.
The Up/Down arrows allow to select a book, and Shift+Up/Down arrows select a sequence of books.
Ctrl-Up/Down goes to another book, and then press the space bar to select that particular book.
For example:
Move the cursor to the book you want to choose.
Use the spacebar to select the book.
Use Ctrl (keep it pressed) and move with the arrow-keys to another book.
Use the spacebar to select this book.
Go to the next book, and when the book is to be selected, press the space bar, and so on.