Which of the following is NOT a method for implementing SAP enhancements?

Function groups are indeed not a method for implementing SAP enhancements. Instead, function groups are used in the SAP ABAP programming environment to define and organize related functions, including function modules. They serve as a container for grouping related functionalities but do not inherently facilitate enhancements or allow custom code to be added to standard SAP functionality.

On the other hand, user exits, BAdIs (Business Add-Ins), and enhancement points in standard code are recognized methods for enhancing or modifying the standard behavior of SAP applications. User exits allow developers to insert their own code at specific points in the standard SAP programs, BAdIs provide a more flexible and object-oriented way to implement enhancements without modifying the original code, and enhancement points let developers add code within the SAP standard code without changing the standard delivery. Each of these methods enables customization and extension of SAP functionality while adhering to best practices for software development.