EditTab Order 

Modifies the tab order of the components on the VCL Form, or within the selected component if that component contains other components.  

For example: a Form containing an edit control with the Tab property value of 0, and a button with the Tab property of 1, the edit control comes before the button when you cycle through the controls with the Tab key. The Tab Order dialog facilitates changing the values of the Tab property using the Up and Down arrows instead of explicitly having to specify values for the Tab property in the Object Inspector.  

Click the Up arrow to move the component up in the tab order, or click the Down arrow to move it down in the tab order.