  We present an analysis of the process
$e^{+}e^{-}\to\pi^{+}\pi^{-}\Upsilon(nS)$ (where $n$ = 1, 2, or 3)
reconstructed in $19.6\rm$ $\rm fb^{-1}$ of Belle II data during a special run
of the SuperKEKB collider at four energy points near the peak of the
$\Upsilon(10753)$ resonance. By analyzing the mass distribution of the
$\pi^+\pi^-\Upsilon(nS)$ system and the Born cross sections of the
$e^{+}e^{-}\to\pi^{+}\pi^{-}\Upsilon(nS)$ process, we report the first
observation of $\Upsilon(10753)$ decays to the $\pi^{+}\pi^{-}\Upsilon(1S)$ and
$\pi^{+}\pi^{-}\Upsilon(2S)$ final states, and find no evidence for decays to
$\pi^{+}\pi^{-}\Upsilon(3S)$. Possible intermediate states in the
$\pi^+\pi^-\Upsilon(1S,2S)$ transitions are also investigated, and no evidence
for decays proceeding via the $\pi^\mp Z_b^\pm$ or $f_0(980)\Upsilon(nS)$
intermediate states is found. We measure Born cross sections for the
$e^{+}e^{-}\to\pi^{+}\pi^{-}\Upsilon(nS)$ process that, combined with results
from Belle, improve the precision of measurements of the $\Upsilon(10753)$ mass
and width by nearly a factor of two to $(10756.3\pm2.7\pm0.6)$ MeV/$c^2$ and
$(29.7\pm8.5\pm1.1)$ MeV, respectively. The relative ratios of the Born cross
sections at the $\Upsilon(10753)$ resonance peak are also reported for the
first time.
