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