Send Backward
Moves the selected object down one level, so that it is closer to the bottom of the stacking order.
Choose Format - Arrange - Send Backward (Collabora Office Writer, Collabora Office Calc).
Choose Shape - Arrange - Send Backward (Collabora Office Draw).
CommandCtrl+minus sign (Collabora Office Impress, Collabora Office Draw)
Open context menu - choose Arrange - Send Backward (Collabora Office Impress).
Send Backward