This view window is set to the 'structural' view, with the raw hex display suppressed:
The hex on the left can be edited just like the the hex in the 'Normal' view. The contents of the structure columns to the right will be automatically updated as this is done.
Clicking on the header of a structure column changes the way that element in a structure is displayed:
You can enter data into the grid formed by the structure display just as you would into a grid control; press a key on a selected cell to begin editing it, press ENTER to signal the end of an edit, navigate between cells with the cursor keys.
Because AXE can tell when you have finished typing into a string field, it moves the selection on automatically once you have filled the field with enough characters.
Most documents do not consist of one structure all the way through. It is therefore particularly useful to associate a structure with a bookmark, so that the correct structure will be selected when you jump to the bookmark.
Although you can't drag and drop the values of structures directly, when you select a group of structure elements the selection is also visible in the hex column. Use TAB to switch focus back to the hex column, and then drag the bytes wherever you want.