Customize the requisition page for non catalogue request

Summary

Set certain fields on PR page mandatory

Content

Hi all
I have a question regarding customizing the requisition page.
Do you know if the page/apps composer can make certain fields mandatory on the PR page?
i.e: Hide 'New supplier' and make supplier, supplier site rendered and mandatory and email when site is provided.

I read an Oracle doc that some pages are not customizable, is PR one of them?

Thank you !