Is there a feature in UX pages that allows us to track modification made by the users?
Modifications?? If that means building their page then End users can only modify "My Pages" and can not make changes to Pages in Apps. Since "My Pages" are personalized dashboards they belong to you, there could be no one except you to make changes to it.
But if you are referring to Changes in the Data on App Pages then yes you can right click on the cell and click " Show History" it is going to open up a window which displays all the changes made.
Hope that helps