Selective removal of un-fixed tracks after auto-routing.

I often manually connect some areas on the board, when I am quite sure autoroute will make a hash of them.  I set these as "fixed", then use autoroute to see how the rest of it might work without changing anything. 

Later I want to get rid of all the newly created tracks and leave the fixed ones.  Doesn't seem to be a way to do this other than manually selecting tracks and deleting them. A simple filter option would be a good idea?  ie  to select only unfixed routes for removal.

This could be part of generally improved selection options using the sidebar.