  We present the calculation of the contribtuions from the chromomagnetic and
four-top-quark-operators within Standard Model Effective Field Theory (SMEFT)
to Higgs boson pair production in gluon fusion, combined with full NLO QCD
corrections. We study the effects of these operators on the total cross section
and the invariant mass distribution of the Higgs-boson pair, at $\sqrt{s}=13.6$
TeV. These subleading operators are implemented in the generator ggHH_SMEFT, in
the same Powheg-Box-V2 framework as the leading operators, such that their
effects can be easily studied in a unified setup.
