Currently Origin's pie chart doesn't support subgroup handling. However, you can do the following like for the sample below:
1) Create two pie charts - one with consolidated subgroup members (left), and the other with subgroup members and the rest consolidated (right). In the later chart, you explode the "rest" part so that the subgroups are held together. 2) Merge two graphs, and adjust the positions to match each other. 3) Using transparency, show the colors in the behind layer (as currently "No Color" is not supported for each section).