I can’t close this shape and its driving me bonkers

0. Make a duplicate of the oval shape and move out of the way for safe keeping.
1. Using Node Edit, make sure that the two nodes at the ends of the backdrop design snap to the oval boundary
2. Select the oval shape using Node Edit tool, make sure that the backdrop is not selected
3. Hover over the intersection point of the backdrop shape and oval, use I to insert a node at the intersection.
4. While still in Node Edit, use D to remove the adjacent line segment outside the desired closed shape
5. Repeat steps 3 and 4 for other end of the design
6. Select bottom curve of oval and add the backdrop shape, then Edit->Auto-join selected shapes. This should leave you with a closed shape.
7. Reposition duplicated oval shape from step 0