I can invision a faded outline around the trace being routed or the via being placed that would show you how close you should be to other traces. It would be defined by clearance in the DRC. It would be a sort of pre-DRC. I have found myself doing a DRC every couple of traces in really crowded designs. This is already sort of done with the follow-me, but I have not been able to use that, for some reason it is really slow for me.
