I just realized that there are two ways to do same thing in Invoices. As it’s a feature that could look cool for developers (two ways to get to the same thing done!), I know ‘standar users’ well enough to assure that it’s confusing for them having too many options. Also in the time of minimalistic, clean and simple interfaces the less you have, the better it looks.
In my opinion, the ones that should be removed are the “add new row” and “add product” next to the save button.