You get a "Create Modification" dialog box and a message template when creating the long text of a message.
You create message HRGB_GBRTI / 131 manually by following the steps in note 2332532:
1. Start transaction SE91
2. Enter the message class as HRGB_GBRTI
Create Message 131:
3. Enter message number 131, followed by the text "Start date found but other required fields are missing. Check long text"
4. This message requires a long text, so uncheck the Self-Explanatory box and press the Long Text button on the menu.
When clicking on the "Long text" button, the below dialog box appears:
In the standard system, any long text/documentation that is created counts as a ‘modification’ and has a template such as the below one. This template may look different to the message you are trying to create.
You have 2 choices:
1) Input the long text as best as possible, and make sure that the message goes back to SAP standard when SPAU is run after loading the relevant HRSP.
The “Z*” modification cannot be deleted once created, only where it is referenced.
2) Ignore inputting the long text, just enter the short text and then make sure that the message goes back to SAP standard when SPAU is run after loading the relevant HRSP.