Yes, there is. When importing large Excel data sets, set option "Layout" on tab "Presentation" of the Excel Import settings to value "None". Note, this will result on all nodes centered on coordinates (0,0) (and thus may look like only one node was created. After the import, save the diagram as GraphML. Then run a layout algortihm suited for large graphs (e.g. "Layout" -> "Organic" is fairly fast even for lots of nodes and edges).