Choose Format - Arrange - Send to Back (LibreOfficeDev Writer, LibreOfficeDev Calc).
Choose Shape - Arrange - Send to Back (LibreOfficeDev Draw).
Shift+KomandaCtrl+minus znak (LibreOfficeDev Utisni, LibreOfficeDev Nacrtaj)
Open context menu - choose Arrange - Send to Back (LibreOfficeDev Impress).