To restrict the PO schedule DFF as Read only in supplier portal

Summary:

To restrict the PO schedule DFF as Read only in supplier portal, there is no option to put an EL expression

To restrict fields and DFF as read only in supplier portal not working it impacts buyers profile too
Request delivery date and promise delivery date (standard fields) to disable it in supplier portal
Restrict Request ship date DFF as Read only
Promise ship date DFF as supplier can edit this one

There is no option to page customize the DFF in supplier portal.

Used EL expression for standard fields supplier portal role

Request delivery date and promise delivery date (standard fields) to disable/hide it in supplier portal- does not work