I go to the Editor Window | run a query | Data Grid area | click on the 'small' icon named "Click here to show/hide columns" (located in upper left most corner of the Data Grid window, not the main Toad window).
I then un-check all the boxes for the columns headers in the Data Grid. This will hide or not show anything in the Data Grid area. But now there is no option to check or select them again. I will have to exit and restart the Editor Window just to see my data again.
Right-click the blank area of the Data Grid and choose "Reset Columns". This will bring back all the columns again in the Data Grid.