This seems to be something that me, heiko and moggi likely forgot during our design session for the chart sidebar. It was something that the sidebar didnt fullfill and i had to open the dialog.
What is primarily needed from the dialog is the data range text field and selection button, data series axis (rows or columns), and checkboxes for first row and column as label. The data series axis and first row/column as label options could be drop down lists rather than radio buttons and checkboxes, which would result in the content panel having 3 lines of content.
Will not be implemented for 5.1
Actually I think that it is not something that should be implemented at all.
Let us close it for now to make it easier to keep track what needs to be done for 5.1.