Yes, you can modify transactions related to GSTR 1 and GSTR 2 after filing them. To modify them: you will first have to amend the transactions manually under section 9A and 9C of GSTR-1 in the GST portal.
Once that’s done, reach out to firstname.lastname@example.org and we’ll mark the GSTR1 and GSTR2 as unfiled. After the GSTR 1 or GSTR 2 is marked as unfiled, you will be able to modify it’s related transactions in Zoho Books.
and GST filing.