I did the following:
What should I do to select dynamically the configuration? - Example:
Use DO_CONFIG_DETERMINATION
event of your view, and place something like this:
IF <ComboBox.Value> EQ "A".
CALL METHOD me->set_config_keys
EXPORTING
iv_object_type = 'your_object_type'
iv_object_sub_type = 'your_sub_obj_type'
iv_propagate_2_children = abap_false.
ELSE.
...config B
ENDIF.
Here object and subobject types are the ones you were prompted while creating custom configuration.
The sample implementation of this method one can find in BP_HEAD/AccountDetails
standard WebUI component.