SAPs default tab-control (also called tab-order) follows on of two scenarios
While both of these methods are correct, they tend to give additional tabs needed before you reach the wanted field.
The tab control system allows you to change the (As an example, on the BP master data if you don’t use the foreign name field you can make a new tab control that skips this field and save you a tab click)
NB: Tab control only work on header level fields. You can't include Tab Control on line level