I was just about to add this (auto-highlighting) as a request myself, so seconded. It would be handy if it could automatically highlight the net as you went to create/edit the track and automatically deselect it when you've finished. Like Peter says, you can use shortcut keys to do it manually but I find myself doing it quite regularly and it would be great if it was fully automatic as it is in Eagle and Altium (where it is accompanied by groovy fade in/fade out). As it is automating existing functionality, surely not a big request ?