  A search for supersymmetry through the pair production of electroweakinos
with mass splittings near the electroweak scale and decaying via on-shell $W$
and $Z$ bosons is presented for a three-lepton final state. The analyzed
proton-proton collision data taken at a center-of-mass energy of $\sqrt{s}$ =
13 TeV were collected between 2015 and 2018 by the ATLAS experiment at the
Large Hadron Collider, corresponding to an integrated luminosity of 139
fb$^{-1}$. A search, emulating the recursive jigsaw reconstruction technique
with easily reproducible laboratory-frame variables, is performed. The two
excesses observed in the 2015-2016 data recursive jigsaw analysis in the
low-mass three-lepton phase space are reproduced. Results with the full dataset
are in agreement with the Standard Model expectations. They are interpreted to
set exclusion limits at 95% confidence level on simplified models of
chargino-neutralino pair production for masses up to 345 GeV.
