Invoice templates can be customized to the own CI
Use placeholders to dynamically insert e.g. client company name etc. into the invoice template
PDF and Email
Choose between only creating PDF invoices or also email those invoices
This is a Google bug. Just reload the page, then all menu items will show up.
This is also a Google bug. The cause for this error message is, that multiple users are logged in within the browser. Just log out with all users, except the one which should be used to work with the addon.