When I want to add a field to an existing request type, I'll get a message box "(KCRT-40074) stating this request type is already being used in # request types. If you want to make changes ...... Instead, it is strongly recommended that you copy this request make changes to the copy ...... use the new request type after making changes".
How does this work? Each time a modification is needed a new request type has to be created? What would be the naming convention? Is there a manual on error messages?
I'm not aware of any manuals on the error messages. This particular message appears anytime to try to make any changes to a Request Type (or Header Type) that has already been used in a Request. If you make a copy of the Request Type, any existing Requests that are using the old Request Type will not see the updates. Generally, I've not had any problems adding fields to existing Requests, or even disabling fields that are no longer necessary. You run into issues when you trying moving the parameter that a field is using or deleting a field and then re-using the parameter that the deleted field was using. It's a matter of data integrity. Deleting a field from a Request Type will not delete the data in any existing Requests that have already been created. Likewise, moving the parameter that a field is stored in will not move the data in the database.
Basically, this is just a warning message to make you realize that any changes you make could have implications to existing Requests that have been created using the Request Type you now wish to change.