Yes you can transfer the balance available in cash ledger of IGST to CGST/SGST but you can't transfer input of IGST to CGST/SGST but there is still a way to do that. Let me help you with this. check your inbox.
You can transfer the balance available in cash ledger of IGST to cash ledger of CGST/SGST.
You can't trasfer the IGST credit ledger balance to CGST/SGST credit ledger, And there is no need to trasfer the same as you can use IGST credit to pay you CGST/SGST output liability.