Suggestions:
Yes, We can save Misc Credit/Debit Note without Item Series. Item series is not mandatory for Misc Credit/Debit Note.
We can use a miscellaneous credit note to make customer account adjustments and non-Inventory related corrections to Sales or miscellaneous charge invoices. It is a credit memo for adjustments to a customer’s account. You can use them to reduce owed amounts on other invoices or to simply credit a customer’s account. It is also used when you void a service invoice.
A misc debit is an accounting entry that results in either an increase in assets or a decrease in liabilities on a company’s balance sheet. In fundamental accounting, debits are balanced by credits, which operate in the exact opposite direction. It is similar to a miscellaneous charge invoice except that it is used to adjust customer accounts.
Hence, System does not hold item series details in Misc Credit/Debit Note.