The history file gives you a text readout of all of the tasks taken by a user on a particular scan/design.

The history is stored on each scan and design. 

The bottom left bar shows the history tab on the left, and the last action taken next to it. In this example, the last action was creating a shell of 3mm on the Scan 1 object.
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Click the History tab, to open a full view of previous actions. 

You can also find history in the scan details, by clicking on the blue URL of a scan or design name.