gtk:grid-attach-next-to (grid child sibling side &optional width height)

grid -- a gtk:grid widget
child -- a gtk:widget child widget to add
sibling -- a gtk:widget sibling widget of the grid that child will be placed next to, or nil to place child at the beginning or end
side -- a gtk:position-type value with the side of sibling that child is positioned next to
width -- an optional integer for the number of columns that child will span, the default value is 1
height -- an optional integer for the number of rows that child will span, the default value is 1

Adds a child widget to the grid. The child widget is placed next to sibling, on the side determined by side. When the sibling argument is nil, the child widget is placed in row 0, for left or right placement, or column 0, for top or bottom placement, at the end indicated by side.