I can definitely share some knowledge on how to manage the reconciled income, @1989684.
First, you'll have to manually unreconcile the transaction by removing the R status before making changes to it. Follow these to do so:
Open the Accounting menu.
Select Chart of Accounts.
Locate the account and click on Account history.
Find the transaction and click on it.
Under the check column, click on the R status until the field is showing blank.
Once done, select Save to completely unreconcile the transaction.
Click Yes to confirm.
Here are some snapshots you can refer to:
Reconciled
Unreconciled
After that, you can make the necessary adjustments. Last but not least, make sure to reconcile the transaction back to maintain the accuracy of the account balances. You can do that by manually changing the status back to R.