Issue - Bind Parameter Values are not visible in expression builder on SO

Our client has requested to show the Discard draft option on conditional basis which is available under actions dropdown on edit Sales Order screen.

When we are trying to achieve this using Page Composer through Sandbox, Binding Parameters option in the expression builder of a show component property is showing blank in the dropdown.

When we tried the same option in some other page like Customers dropdown shows proper list of values.

please help.

Thanks in Advance..!!