The BAdI implementations of the enhancement concept are not treated as standalone objects; instead, they are integrated in the overall concept. Consequently, the tools for implementing BAdIs are part of the Enhancement Builder integrated in the ABAP Workbench.
Transaction SE19, up to now the only entry point for implementing classic BAdIs, now administers classic and new BAdI implementations. When displaying/changing an existing BAdI implementation, it analyzes whether the BAdI is a classic or a new one and then switches to the respective tool, which is the enhancement implementation editor for a new BAdI. Implementing classic BAdIs is still supported.
Since the classic SE19 transaction represents only a side entry point into the Enhancement Builder, you can also use the Object Navigator (SE80).
For more information about how to create enhancement implementations for BAdIs, see Creating, Editing, and Deleting Enhancement Implementations.