This is insane! Which product team of Zoho books added the feature for estimates to non-editable after a transaction conversion?

In certain industries as the user below my thread correctly points out, we need constant edits to BOTH the invoices and estimates to changing demands! Which ridiculous software does not allow their users to edit their estimate after conversion? 

Should we return to paper and pens? That way we can still edit our quotations! 

Please disable the feature immediately and add this as an option if need be, i am sure i am not the only angry customer with this absurd feature.