  Time-domain and multimessenger astronomy (TDAMM) involves the study of
transient and time-variable phenomena across various wavelengths and
messengers. The Astro2020 Decadal Survey has identified TDAMM as the top
priority for NASA in this decade, emphasizing its crucial role in advancing our
understanding of the universe and driving new discoveries in astrophysics. The
TDAMM community has come together to provide further guidance to funding
agencies, aiming to define a clear path toward optimizing scientific returns in
this research domain. This encompasses not only astronomy but also fundamental
physics, offering insights into gravity properties, the formation of heavy
elements, the equation of state of dense matter, and quantum effects associated
with extreme magnetic fields. Magnetars, neutron stars with the strongest
magnetic fields known in the universe, play a critical role in this context. In
this manuscript, we aim to underscore the significance of magnetars in TDAMM,
highlighting the necessity of ensuring observational continuity, addressing
current limitations, and outlining essential requirements to expand our
knowledge in this field.
