Choose Format - Arrange - Send Backward (LibreOfficeDev Writer, LibreOfficeDev Calc).
Choose Modify - Arrange - Send Backward (LibreOfficeDev Draw).
ComandoCtrl+segno meno (LibreOfficeDev Impress, LibreOfficeDev Draw)
Open context menu - choose Arrange - Send Backward (LibreOfficeDev Impress).