Here is an example of what I am talking about: 
1. Create a new node using the "Process" template from the "Flowchart" palette section.
2. Choose the desired color as "Fill Color 1" and "No Color" as "Fill Color 2".
3. Copy the configured node.
4. Set the desired label text for one of the two nodes.
5. Move the node with text (completely) over the node without text.
6. Right-click the node with text and choose "Convert to Label" from the context menu.
7. In the properties view, change "Placement" to "Internal: Bottom Left".
8. In the properties view, change "Distance" to e.g. "10".
If you want to stack more than two nodes, create additional copies in step 3 and repeat step 5 to 8 as necessary.
(Thanks to Thomas Behr for this workaround!)
As you can see, a node of this type is extremely useful! IMHO, yEd should have it by default.
