Answer
Build the parameter attribute string using Client_SYS, the same way you would for many other deferred/parameterized calls: Client_SYS.Clear_Attr(attr_), then Client_SYS.Add_To_Attr('PARAM_NAME_', value_, attr_) for each parameter the target procedure expects (matching its actual parameter names), then pass that attr_ string as the 'PARAMETER' argument to Transaction_SYS.Deferred_Call, for example: Transaction_SYS.Deferred_Call('Your_API.Your_Procedure', 'PARAMETER', attr_, 'Job description', sysdate, 'FALSE'). This is the standard pattern for passing normal, simple parameters (not just message-object-style calls) through a deferred background call.