Test Design Studio makes it easy to keep up with modifications made to an existing document. These changes are tracked after a document is first opened.
As you make changes to your document, the margin for all modified lines will turn yellow. If you later save your document, the margin will change from yellow to green. This indicates lines that have been modified since the document was opened, but have been successfully saved to the file. As you modify the document after the save, you will continue to see yellow indicators in the margin until the changes are saved.
Note: This feature can be turned on/off using Text Editor General Options.