Unable to Personalize PO Charge Account in Change Order as Sandbox Field is grayed out

Summary:

Hello , we have requirement to make the field (PO charge Account) editable for users having a specific custom role and for rest users it should be Readonly , on page Edit> Purchase Order.

Issue: when we are trying to get the above requirement through the Sandbox Structure , Edit field is alone Disable (Field : PO charge Account) so unable to even set up condition .

We tried updating KFF component available above the required PO charge account field but still no Luck , can you please let us know how Edit properties can be enabled/opened for this Field and is there any reason why this field is graded out for Edit