Background Information
When you click the Insert Column button in the Columns section of the Format ribbon, the button does nothing. This button is supposed to display a list of standard and custom fields for the type of view displayed. For example, with the Gantt Chart displayed, clicking the Insert Column button should show the list of default and custom task fields.
Resolution
Click File > Options to display the Project Options dialog. Click the Advanced tab to display the Advanced page of the Project Options dialog. Scroll down to the Edit section of the Advanced page. Select the "Edit directly in cell" option and then click the OK button. If the "Edit directly in cell" option is not enabled, you cannot insert columns using the Insert Column button on the Foramt ribbon.