Create a group from selected nodes. Adds a new compound node to the UGM; sets _parent on children.
_parent
the new group node ID
Get info about all groups.
Get all children of a group.
Check if a group is collapsed.
Remove a group; children become ungrouped.
Toggle collapsed state.
Create a group from selected nodes. Adds a new compound node to the UGM; sets
_parenton children.