Vertically centres the selected objects. If only one object is selected in Draw or Impress, the centre of the object is aligned to the vertical centre of the page.
To access this command...
Choose Format - Alignment - Centred (LibreOffice Writer, LibreOffice Calc)
Open context menu - choose Alignment - Centred (objects selected) (LibreOffice Impress, LibreOffice Draw)
On Align toolbar (LibreOffice Impress, LibreOffice Draw), click
Centred
To align the individual objects in a group, choose Format - Group - Enter Groupdouble-click to enter the group, select the objects, right-click, and then choose an alignment option.