Queries edited by SAP GUI 7.4 is not editable in lower versions of SAP GUI such as 7.3 .
There may be some solutions like reinstall lower versions or apply some patch .But these are not quick ones and also not feasbile .
Developer may be in peril sometimes about this and so below workaround will help you to resolve this and make the query again editable with lower versions .
So please follow the attached doc to resolve this .