How can I select neighbors?

You can use TraceNeighbor to highlight neighbor nodes, then convert highlight to selection.

Step 1, click on “Trace neighbor” icon, drag slider to 1 or more

Step 2, click on “Select Visible Nodes” to convert highlight to selection

From here, you can tag those nodes as neighbors
by clicking on the image icon.

Then in Tag view, you can click on the tag to select them again.

If you want to keep only those neighbor nodes, you can click on “Invert Selection” icon image, which has a small number showing how many nodes are selected, then hit “Delete” key to remove all non-neighbor nodes.