void updateSelectionSequence(FieldLocation point) {
			if (!selectionOn || anchorPoint == null) {
				return;
			}
			if (scrollPoint != null) {
				updateSelection(removeFromSelection);
			}
			scrollPoint = new FieldLocation(point);
			updateSelection(!removeFromSelection);
			notifyLiveSelectionChanged();
		}
Checks if the "control" modifier is on and the "shift" modifier is not.
Ghidra/Framework/Docking/src/main/java/docking/widgets/fieldpanel/FieldPanel.java