Altium 20 autoroute via polygon
I would create test points (in the schematic) that are the width of the traces with nothing but copper for the footprint, then place them where you want the traces to go. (not a great solution but one that works). If the autorouter sees the pads in the polygon then it will try to route the traces there.
However, the autorouter is difficult to use and does not do what you want it to, I've found it's easier to use the multi route option and route by hand.