Additional Custom Fields

I know this question has been asked before but I’m still at a loss on how to proceed.
I’m self-hosted and white labeled.
I’m trying to add several additional custom fields on my invoices.
These fields will be for internal reports and I want them to be hidden from the printed invoices.

Do I have to rewrite the entire code regarding the handling of custom fields?

Any help would be greatly appreciated.


Maybe you can store more than one value in a single custom field?

Not sure what else to suggest…

That was my first approach.

Now I’ve been trying to sift through the code to see where the fields are created dynamically.