Why would you want to do this?
Invoice ID is the table's Primary Key--not something that you want to mess with as an error here can screw up how Invoice records link to other records in relationships.
There are, however, a number of ways that you might get such a value set up in a different field. But why you might do so is a detail to consider in how (or if) such an option might be added to the starter solution in question.
Because I want each customer to have their own set of invoice numbers. Each customers subsequent invoice would make sense numerically. So Customer A would get Invoice #1 for their specific use case. I don't want their next invoice to be #37 if I have only invoiced them a second time. It doesn't make numerical sense.
That's not really the purpose of the Invoice ID field. It serves as a unique identifier of each invoice.
But you could add another field that provides such a sequence and it can be the visible number on your layouts while the Invoice ID can remain hidden.
You can add a field to the Customer table that you increment with each new invoice created. This field can then be the visible invoice number with a series of values specific to each customer.
I'll give that a go. Thank you.