Required library edition: 
Required library file: dhtmlxgrid_drag.js
set Drag-And-Drop behavior
mode - behavior name
child - the item is dropped as a child of the target item;
sibling - the item is dropped as a sibling of the target item; if drop occurs between the parent and the child elements, the item is moved on the parent level;
complex - the item is dropped as a sibling or a child depending on the position of the target item towards the landing; if drop occurs between the parent and the child elements, the item is moved on the parent level;
sibling-next - the item is dropped as a sibling of the target; if drop occurs between the parent and the child elements, the item is moved on the child level;
complex-next - the item is dropped as a sibling or a child depending on the position of the target item towards the landing; if drop occurs between the parent and the child elements, the item is moved on the child level.
mygrid.setDragBehavior(sibling);
See also: setDragText