DotSimplifyRelations is an option for
DotSimplify. Its setting may be a list of substitution
rules of the form
DotSimplifyRelations -> {a.b -> c, b^2 -> 0, ...}.
In the rules, Condition should not be used and patterns
should be avoided on the right-hand sides.
Notice that the performance of DotSimplify scales very
badly with the complexity of DotSimplifyRelations and the
number of terms of the expression.