This editor allow you change Tab order of controls. Tab order - this is order of switching focus between controls with Tab button. Because in Autoit order of switching the same as controls creating order, using this editor will affect controls creation order in result code.
You can change order with drag'n'drop or with buttons at right side of dialog.
Internally, this will change TabOrder property for controls, so if you want you can change this property manually.
Each line have a number at right of icon - this is old tab order for your reference.
Note, that in container controls (TabSheets and Group control) numeration is independent from global form Taborder numeration. TabOrder count is start from 0.
When you select some control and open TabOrder editor, you can change order for all controls, that have the same parent as selected control. You can easily see ierarchy of objects in the Objects Tree View, each node mean parent level raised up.