Add a ROW with aggregated data to pivot table and display on a chart

My raw data contains Level 1,2,3,4 I am able to create a pivot table showing all levels in a bar chart, however I am having trouble showing a sum of Level 3 & 4 in a new row on the pivot table that I am also able to display on the chart. The pivot table is very restrictive and I am unsure of the best method to add this row to the pivot table. Any help or guidance would be greatly appreciated.

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