Fusion Self Service Procurement customization for Suggested Buyer

Summary:

We have a requirement to make Suggested Buyer field in the Edit Requisitions page required for all lines.

Sandbox customization with Required checkbox is not covering the lines that are not clicked and loaded on the page. Customization does not work unless user clicks on the requisition line and goes through every line.

Is there any way to achieve this requirement for all lines in another way? In EBS we used POR_CUSTOM_PKG to achieve such requirements at the code level. Does the Fusion Self Service Procurement has anything similar ?

Version (include the version you are using, if applicable):