This is OOB functionality in SugarCRM that, any type of user cannot delete opportunities having sales_stage: Closed_Won OR Closed Lost (Delete button becomes disabled)
I need to to add more sales_stage values in this functionality and for the purpose I found below 2 files
The issue is if I copy the core files in custom and apply the changes than changes are not working but if I change direct core files than only changes are working successfully and this is not upgrade safe.
In this situation how can I achieve the required functionality.
Any help will be highly appreciable