When editing a Graph as an Author in Lt, why can't I define the graph and axis titles?

The X & Y Axis titles on a Graph in Lt are only available to edit once there is valid data plotted. For example, if a Table you are plotting has only the Column Titles, and no numerical data, you will not be able to edit the Axis Titles. Add some 'dummy' values to your Table so data is plotted - this will allow you to access the Axis editing dialogue: