I'm running a saved search on Invoices and I want to display all the currencies a customer has been invoiced in, in one row. I can get the number of currencies a customer has been billed so far, but can I reflect all these currencies in one row/line?

I don't think that's stored in the customer record directly, which will make it hard. What you might want to do instead is have a custom field on the Customer record where you store this information. Populate it via a script or workflow. Not ideal, though.

I think If you do a transaction main line search group by customer. You could do a formula numeric summary column for each currency to total up the invoice count for each currency. Something like case when {currency} = 'USD' then 1 else 0 end. You would just add a column for each currency you offer.

we have about 20 currencies being used, I think having a formula for each currency won;t be very ideal

Do you just want a list, as in "USD", "AUD", "EUR" etc? You could probably use

NS_CONCAT

/

LISTAGG