Provide a facility to customise headers in Excel and CSV export

This was recently raised as a question. At the moment you can choose whether or not to have a header row when exporting to a CSV file or Excel, but you have no control over the heading row text which is always "Level 1", "Level 2", etc.

Of course it is possible to edit or add the headings in Excel, but it's a hassle, especially if you are doing multiple exports of the same map and even more so if the you decide to change the heading names in some way each time.

It would be helpful if there was a facility to customise headings, either on the fly or by applying a set of stored headings. With either option the heading set should be able to be saved in the map.