You'll probably want to edit your data structure once in a while. If you want to edit an element of the data structure, click on "Templavoila", click on "Storage folder", click on the "Page templates" tab (if necessary) and click on "Update mapping".
Then, click on "Modify DS/TO". A warning message will appear, which says that the Templavoila configuration tool might overwrite changes that were applied manually. We've not done that. Yet. So proceed without fear!
You'll enter the screen that you've last seen while creating the data structure. You can edit the separate data elements by clicking on the edit icon on the right. You can also add new data elements like you have done in one of the previous steps. When you add a new data element, you also need to map it. Don't forget to click on the "Save" or "Save and exit" button to save your changes.
Some things you cannot change with the method above. If you want to change the name of the data element (for example "field_top_header_left"), or you want to change the order of the data elements in the data structure, you'll have to manually edit the data structure. You do that by clicking on the Templavoila item in the web menu, then click on "Storage folder" in the page tree. After that, click on the edit icon next to the title of the data structure:
You'll see the xml code of the data structure. Yeah, I have to admit that's quite scary at first. To edit the field name of the data element, edit both begin and end tags, in this case "field_top_header_left". These are indicated by red squares. To move the entire data element, cut and paste everything between and including the start and end tags of the data element (indicated by the large red square) to a desired position.
Be aware that you leave the nested structure of the xml code intact. Don't forget to click on one of the save buttons, to save changes.