When modeling, there is currently no concept that represents what we do not yet know. A modeler often needs to sketch a silhouette of a missing piece and show how it connects to known facts.

Proposed enhancement:

• Add support for an Object/Fact Type carrying a 'gap' element concept (e.g. otft[concept] with elm concept 'gap'), so the modeler can mark an OTFT as representing an unknown.
• Alternatively, introduce a dedicated container shape with curved/sketchy outlines that surrounds connected OTFTs and visually signals the gap.

This would allow modelers to communicate uncertainty and incomplete knowledge directly inside the diagram instead of working around it.