Check this post : https://blogs.sap.com/2019/09/23/customizing-material-master-adding-new-tabsub-screen-in-mm01-mm02-mm03/
How to debug a background job ?
In SM37, type JDBG (like Job Debug in Background).
Read MoreConfigure the pretty printer
In transaction where you can edit code (like SE38, SE80…) :
Create a BADI
Refer to the links below :
Building Your First BADI
How to Implement a BADI
How to use filter in a BADI