  It is known that for N=8 supergravity, the double-soft-scalar limit of a
n-point amplitude is given by a sum of local SU(8) rotations acting on a
(n-2)-point amplitude. For N<8 supergravity theories, complication arises due
to the presence of a U(1) in the U(N) isotropy group, which introduces a
soft-graviton singularity that obscures the action of the duality symmetry. In
this paper, we introduce an anti-symmetrised extraction procedure that exposes
the full duality group. We illustrate this procedure for tree-level amplitudes
in 4<=N<8 supergravity in four dimensions, as well as N=16 supergravity in
three dimensions. In three dimensions, as all bosonic degrees of freedom
transform under the E8 duality group, supersymmetry ensures that the amplitude
vanishes in the single-soft limit of all particle species, in contrast to its
higher dimensional siblings. Using recursive formulas and generalized unitarity
cuts in three dimensions, we demonstrate the action of the duality group for
any tree-level and one-loop amplitudes. Finally we discuss the implications of
the duality symmetry on possible counter terms for this theory. As a
preliminary application, we show that the vanishing of single-soft limits of
arbitrary component fields in three-dimensional supergravity rules out the
direct dimensional reduction of D^8R^4 as a valid counter term.
