Hello Fenil,
1. First find the Structure which is bound to the Entity LEAVEAPPROVAL.
You will see the below line of code.
Example ->
lo_object->bind_structure( '/IWBEP/CL_MGW_RT_SFLIGHT=>TY_S_SFLIGHT' ).
2. Now go inside that Structure and Add the Field there.
3. In the MPC Class go inside DEFINE Method and add the property.
lo_property = lo_object->create_property( iv_property_name = '<Give Your New Property Name>'
iv_abap_fieldname = '<Filed Name which is newly Added by You in the Structure which is bound to the Entity LEAVEAPPROVAL>' ).
Save and Activate.
4. Clear Model Cache with T-Code /iwfnd/cache_cleanup
Regards,
Ashwin