Document numbering and layout customization

I’m wondering if it’s possible to use a custom numbering format—such as INV-1001 for invoices or PO-1001 for purchase orders—to help distinguish document types. It seems that Manager recognizes numeric sequences and continues them automatically, but doesn’t recognize or retain letter prefixes. Is there a workaround for this?

Also, am I correct in understanding that there is still no way to customize the typeface, color, or layout of customer- or supplier-facing documents? Since the “Themes” feature appears to be deprecated, are there any alternative options for layout customization?

If you search the forum you will find that this topic has been discussed many times