Hi there!
I have recurring expenses that i would like to directly charge to my customer. You already have the option “Should be invoiced” which is great! It would be great if when you mark this field you get a new Textbox with the exact amount you want to charge from that customer.
This would be great so you dont have to go into the invoice everytime and do this manually. If you have a customer for example who has 20 or 30 monthly invoices like this that would be a big time saver 
As said, this is just a suggestion. Thanks!