create a transaction variant through t-code SHD0 for F-48

Hello friends,

I want to create a transaction variant through t-code SHD0 for F-48 where I wanted PO as optional field but system is not allowing me to create and gives an error message " variants are possible only for dialog transactions"

Can any one suggest how to make the PO field as optional in f-48 ?

Thanks and regards,

Ashok Singh