The point of displaying column button and edit button in DataColumn.
It is used in DataColumn.buttonVisibility property.
| ALWAYS | "always" | Always display if the button is set in the column. |
| DEFAULT | "default" | Display if it is a focused or mouse hovered cell. |
| VISIBLE | "visible" | Display if it is a focused cell. |
| CURRENT | "current" | Display if it is a mouse hovered cell. v 1.3.8 |
| HIDDEN | "hidden" | Do not display the button. |