中央揃え (左右)

Horizontally centers the selected objects. If only one object is selected in Draw or Impress, the center of the object is aligned to the horizontal center of the page.

このコマンドの見つけ方

Choose Format - Align - Centered (LibreOffice Writer, LibreOffice Calc).

Choose Shape - Align - Centered (objects selected) (LibreOffice Draw).

On Align bar (LibreOffice Impress, LibreOffice Draw), click

中央揃え（左右）

The vertical position of the selected objects is not affected by this command.