Hello Praneet,
This is quite possible without entering into Enhancement area. See this picture of IMG Customization (Overview of Notifications in SPRO)
Assume your Notification Type is SD and your Catalog Profile is CAPA. Then give the Catalog profile value while configuring the Notification type itelsf like this.
With this, the Code-groups and Code of this profile are defaulted. Means when you click the F4 help button in the any of the Catalogs&Codes Tab of the Notification, these codes only would appear (Means your Code Groups are defaulted). Try it.
This is applicable when you fill the Codes details before filling the Reference Object (Equipment/FunLocn) in the Notification. Once you fill the RefObject the CatalogProfile of that technical Object would be defaulted, if it has one. If RefObject has no CatProfile filled in its masterdata then there is no issue. So, the Codes to be filled first in your SD Notification before you fill the RefObject details.
Try this. Hope this is the thing you are looking for. If you want, some enhancement to force user to fill Codes before the RefObj, I think it can be made possible.
Hope this reply is in-line with your requirement.
Best of luck
Jogeswara Rao K