You can customize Classic report templates. They are located in the folder you designated during installation. If you used the default path during installation, the Reports folder is c:\Program Files\Micro Focus\StarTeam Cross-Platform Client <version>\samples\details-templates\. Note that different clients and client installations on different operating systems will probably have different installation folders. You may need to put templates in more than one location. All the templates are in HTML format.
For example, if the Default report for the file component is the most similar to the new report you want to create, copy all FileDefault.x template files using a name like FileMYREPORT.x. In this case, you would create new files named FileMYREPORT.Name, FileMYREPORT.Title, and so on. In the Cross-Platform Client, the new report would appear in the Report dialog box with the name MYREPORT, along with the original Default report.