Remove All  

Pick this button to Remove All Regions from the list.  The geometry itself is not deleted from the part model.

Remove Active  

Pick this button to Remove the selected Active region from the list.  You can select multiple Regions from the list using the Ctrl key and then pick this button to remove them all.  The geometry itself is not deleted from the part model.

Select Curve/Edge Regions  

Pick this button and the dialog will minimize, prompting you to make a selection from your part.  You can select curves or face edges.  After completing the selection, the dialog will re-appear with your Region selections listed.

Select Surface Boundary  

Pick this button and the dialog will minimize, prompting you Select surface for boundary.  You can select one or more part surfaces.  After completing the selection, the dialog will re-appear with each surface edge boundary listed in the Selected Machining Region(s) list.

Select Pre-Defined  

If you pick this button, the Select Pre-defined Machining Regions dialog will display, allowing you to select one or more Regions.  This operation dialog will then re-appear with your region selections listed. Pre-Defined Regions can be created using the options on the Regions tab of the Machining Objects Browser.