  Ultra-cool dwarf stars are abundant, long-lived, and uniquely suited to
enable the atmospheric study of transiting terrestrial companions with JWST.
Amongst them, the most prominent is the M8.5V star TRAPPIST-1 and its seven
planets. While JWST Cycle 1 observations have started to yield preliminary
insights into the planets, they have also revealed that their atmospheric
exploration requires a better understanding of their host star. Here, we
propose a roadmap to characterize the TRAPPIST-1 system -- and others like it
-- in an efficient and robust manner. We notably recommend that -- although
more challenging to schedule -- multi-transit windows be prioritized to
mitigate the effects of stellar activity and gather up to twice more transits
per JWST hour spent. We conclude that, for such systems, planets cannot be
studied in isolation by small programs, but rather need large-scale, jointly
space- and ground-based initiatives to fully exploit the capabilities of JWST
for the exploration of terrestrial planets.
