Hi Gianni,
You might want to test this out. I've not done this for accruals but I've done it with "legacy" interest or principal cash flows. SAP has t-code TBB1_LC that archives "legacy" postings without generating FI postings. Since you are talking about accruals and I'm assuming you are using TPM44, I believe you should be able to run TPM44 and uncheck "Immediate Posting". This will create new accrual flows under TPM13 with a status of Flagged for posting. Then you can use TBB1_LC to change the status to Fixed. Give that a try in a test environment and see if it works.
Regards,
Anya