Hi
You need to create one class using CL_BSP_WD_TREE_NODE_PROXY as super class. and implement your class with GET_CHILDREN
Call this class in 7th level using below code.(how they it is done in level 7)
lr_child ?= me->node_factory->get_proxy( iv_bo = lr_ent
iv_parent_proxy = me
iv_proxy_type = 'Your 8th level class' ).
Regards,
Deepika.