The auxiliary debug configurations is useful if you need to run several Denodo applications to debug a particular extension. For example, you may need to run both the VDP/ITP Server and the Scheduler Server in order to test and debug a custom Exporter.
For your scenario, I would perform the below steps,
* Open Eclipse and navigate to the Denodo4E Debug Configurations > Denodo4E Configurations
* Create a new configuration for performing the Debug in Denodo Scheduler.
* In the configuration, select the Application as "Denodo Scheduler Server" and click on "ADD" to add the Denodo Extension projects from the Eclipse project’s list.
* Click on Debug and start the [Job](https://community.denodo.com/docs/html/document/denodoconnects/8.0/Denodo%20Email%20Exported%20Files%20Custom%20Handler%20-%20User%20Manual) (i.e., Job which contains custom Handler) from the Denodo Scheduler.
Hope this helps!