Sometimes subcomponent child elements are missing from navigator. This happens at least after the following sequence:

• Add a Component
• Add a Rectangle under the componentRoot item
• Delete component
• Undo deletion
• Select component and press F2 to enter subcomponent edit mode

--> The componentRoot doesn't have rectangle child node in navigator.

The missing node will appear if you make any changes to or even select text inside the rectangle node in text editor.