I can't manually add services and prices for invoices on mobile app?

I’m a freelance musician so my contract prices vary job to job. On the mobile app I am not able to manually type in a new service and add a price. I can only select from past services I’ve sent, and I can’t edit them the way I can on the website version. This means I have to use my laptop to send every contract and slows me down when I’m on the go. It is also impossible to leave the service selection window once that list comes up on mobile. I have to back out of the file and go back in.