I've just loaded the excel file without any transformation:
(ooxml, embedded labels, table is Sheet1);
Then I've created a drill down dimension group GRP in the frontend, with fields [Task 1], [Task 2], [Task 3].
I've created a straight table chart with dimension GRP and enabled option 'Supress when Values is NULL' on dimension tab.
That's it. It's relying on TaskID for parents being smaller than TaskID for children, if this is not the case, you would need to find something else to sort your status by.