As a <user> I want <an undo button> so that <I can easily correct mistakes>.

Context from Helene:

>A new issue about the time stamping. As I mistakenly moved the ruler in one segment, I tried to come out without saving anything to hopefully get back to the previous version, but it did not work. I found out that it has saved the erroneous change. Now I purposely came out of the editing without saving anything after updating the description and tags of another segment and the same happened. In short, it seems that the time-tamping is saving all changes, which may mean that the "save" button is now totally redundant.