Choose \<emph\>Modify - Flip - Horizontally\</emph\> (LibreOffice Draw)
Choose Format - Image, and then click the Image tab
Choose \<emph\>Format - Flip - Horizontally\</emph\>
Right-click a selected object, and then choose \<emph\>Flip - Horizontally\</emph\> (LibreOffice Impress)