Use the Segment History window to view the changes history of the selected segment in the workspace window (also called String list). This history is maintained as part of the TTK but is not leveraged with the translation and metadata.  

Show white space symbols: Toggle to display space characters as a dot symbol. This makes space characters more visible, particularly when comparing differences between two history entries of a segment.

Segment histories are recorded when a change has been made to a segment and the TTK project is saved. The timestamp of changes will thus be at the time of saving the project. Those recorded segment changes are listed chronologically under the date column.

Changes are recorded in the segment history on saving the project if any or several of those occurred:

When multiple entries are listed in the Segment History, press and hold the CTRL key to select 2 segment histories you wish to compare. The Translation 1 and 2 fields will display the 2 segments highlighting any difference in red. This includes space character differences which may not be evident until you select the "Show white space symbols" option.

In the example below, the segment history shows the edits made by user RobH (in red) after the segment was Machine Translated by user cvallin. We can also see the evolution of the segment with the various translation status changes: first machine translated then translated by a user RobH, modified by user JoshZ adding a memo and finally signed off by user SarahW.