gtk-grid-insert-next-to (grid sibling side)

grid -- a gtk-grid widget
sibling -- the gtk-widget child of grid that the new row or column will be placed next to
side -- the side of type gtk-position-type of sibling that child is positioned next to

Inserts a row or column at the specified position. The new row or column is placed next to sibling, on the side determined by side. If side is :top or :bottom, a row is inserted. If side is :left of :right, a column is inserted.