I have a little small engine repair shop, and Gnucash invoices work well if you're selling things, but repair shops need 3 fields on a customer invoice that Gnucash invoices don't have yet:

1 Below customer info we need a field to put a description of the item being repaired.

2 Below that we need a field to record the instructions the customer gave us on what they want done.

3 Below that we need a field to describe the work that we did.

The fields shouldn't have any set length, they should expand to suit the text because depending on what's being fixed, there might need to be more written than you or I could anticipate.

Below that is the list of parts and the labor, which is already fine as it is.

I'm not a programmer, but this seems like it should be relatively easy, it's not messing with the math, it's just adding a few extra text fields, and it would make this software useful to sooooo many more people.