Here is the full list:
1. Book List
Hold Command button + I => Insert Book
2. Page List & Element List
Hold Command button + T => Insert Paragraph
Hold Command button + M => Insert Markdown
Hold Command button + P => Preview
Hold Command button + E => Export As EPUB
Hold Command button + I => Insert Chapter
3. For Fixed Layout Book
Hold Command button + I => Insert Page
Hold Command button + P => Preview
Hold Command button + E => Export As EPUB