Hi, I want to tag a project information on transactions like a purchase order, bill, sales order, invoice etc. Please let me know how to do it. Should I create a custom project field and source the projects into that field? Or a standard field is available to enable. Please need your input on this. Thanks in advance.

Look into WBS that’s what I would use. https://novutech.com/news/advanced-project-budgets/

do you use SuiteProjects (full version of projects) or just basic projects you enabled in your non-SP NS instance?

There should be a line level field for customer/Project for all P2P transactions if project or advance project is turned on