I have looked through the online documentation for CUDD (http://web.mit.edu/sage/export/tmp/y/usr/share/doc/polybori/cudd/cuddIntro.html), a library for Binary Decision Diagrams (BDDs) but could not find a method for turning off the automatic use for complement edges for BDDs. It does seem to me it should exist, do you know whether it exists?
This functionality does not exist in CUDD as the use of complemented edges is implemented as non-optional feature in every single BDD manipulation function.
It is also unclear what use it would have. The functionality of CUDD is not altered by switching off complemented edges. If your interest is to not have complemented edges show up in visualizations of BDDs, it would make more sense to write a visualization function that distinguishes between complemented and non-complemented nodes, which is possible (and has been done before) and gets rid of the complemented else edges.