  Imaging antiferromagnetic 180{\deg} domains with actively controlled
visibility is vital for both fundamental science and sophisticated
applications. While optical second-harmonic generation (SHG) is a well-known
technique for distinguishing such domains in non-centrosymmetric
antiferromagnets, a general material-based strategy to control domain contrast
remains elusive. Using van der Waals antiferromagnet MnPS$_3$ as a proof of
concept, we demonstrate the tuning of nonreciprocity-induced domain contrast in
SHG through applying an in-plane electric field that transforms the magnetic
point group to its unitary subgroup. The interference among intrinsic
electric-dipole, magnetic-dipole, and field-induced electric-dipole
transitions, each carrying distinct characters under space-inversion
($\mathcal{P}$) and time-reversal ($\mathcal{T}$) operations, enables large
tuning of domain contrast and nonreciprocity in a broad spectral range. This
strategy, generically applicable to systems characterized by
$\mathcal{PT}$-symmetric magnetic groups with a polar unitary subgroup, offers
a path to fast electrical modulation of nonlinear nonreciprocal photonic
behaviors using antiferromagnets.
