What does this paintbrush icon mean on NodePaths?

I thought it would be like an eyedropper to pick a node.
Corresponding code:
export(NodePath) var nodepath_body = null
export(NodePath) var sprite_path = null
Edit: Clicking it when the field has a value clears it. Is that all it's for? Clearing an existing value? Why a paintbrush (or is it something else)?