Move to selection mode by clicking on the selection control of the 3D window containing the graph.

Then you can select visible nodes clicking on them. The selected node change color in the 3D window and become selected also in the corresponding browser window. You can select several nodes keeping ctrl key pressed.

You can also select neighbours of a node by choosing select neighbours in right-click menu. A node has neighbours when there are relations between the nodes. So you can select neighbours in a sulci graph where such relations exist, but generally not in ROI graph because there's no link between different regions.

You can undo selection by choosing unselect in right-click menu. This feature undo selection for all nodes currently selected. These nodes retrieve their original color.

Finally, it is possible to remove nodes from the window by selecting them and choosing remove from this window in right-click menu.