Autoreduce is not in the help file, which suggests it has either been removed or renamed.
Searching for "reduce nodes" reveals a similar facility at print time, but it doesn't change the design object, only its rendering at print time. It is on the postscript tab, so presumably is not available for inkjet printers.
Corel probably assumes that modern computers have enough resources to handle complex objects without having to reduce them, but that seems to be missing the point. Reducing the number of nodes often makes for a much smoother looking curve.
On a complex object I find I can often select about 3 nodes in every 4 and delete them, without substantially changing the shape of an object but its rather tedious doing it that way and the old autoreduce function would probably achieve the same a lot faster.