Organizing nodes into groups
To keep your graphs organised, you can create groups. This becomes especially useful as your graphs increase in size.
Creating and adding nodes
To create a group, simply right-click the canvas and select "Add Group". You can then add nodes to it, by selecting nodes and dragging them onto the group. The group node will show a blue indicator, that tells you the selected nodes will be added to the group upon release.
If you want to detach a node from a group, right-click it and click "Detach from group". If you want to remove multiple nodes, select them, right-click and click "Detach Selection From Group(s)".
If you're unable to add selections of multiple nodes, this might be due to the version of Unity you're using.
With some versions of Unity adding a selection to a group won't work, if you have any edges/connections selected.
To work around this, you can hold CTRL while making or selection, to exclude edges from being selected. CTRL+E will deselect edges, removing them from your current selection. This should then allow you to add the nodes.