Choose \<emph\>Format - Alignment\</emph\> (LibreOffice Writer, LibreOffice Calc)
Choose \<emph\>Modify - Alignment\</emph\> (objects selected) (LibreOffice Draw)
Open context menu - choose \<emph\>Alignment\</emph\> (objects selected) (LibreOffice Impress, LibreOffice Draw)