Hi accounts-muttiho,
Welcome back to the Community. QuickBooks is a versatile program that helps you manage your business with peace of mind. I'll be glad to steer you in the right direction.
The ability to merge an invoice isn't available in QuickBooks. I can see the benefit of having this function and I encourage you to send feedback about this to our engineers. You can send feedback by clicking on the Gear icon and looking for Feedback. New product ideas and improvements are based on the feedback we get from users like you.
Let me know if you have other questions by leaving a comment below. I'll be a message away.
