Add New Tab/New Field in WorkItem windows
1. Export the exiting workitem type (xml)
Syntax: witexport /f <filename>.xml /t < Team Foundation Server name > /p <project name> /n <WorkItem Type name>
Example: witexport /f task.xml /t MyTFS /p MyProject /n Task
2. Open the task.xml in an editor
4. Import the modified workitem type (xml)
Syntax: witimport /f <filename>.xml /t < Team Foundation Server name > /p <project name>
Example: witimport /f task.xml /t MyTFS /p MyProject
5. Refresh the Team Project and Add a New Task, you should see the changes as follows: