TRAPPIST-1 discussion and addon for 0.98 is here.

We also can't detect planets which are very far from the star, like Uranus and Neptune. So systems like Kepler-90 may actually have more planets.
Compact systems with many planets packed inside Mercury orbit probably have no external planets (or have just few of them). We can roughly estimate "is the system map complete" by summing up the masses of all known planets and dividing them on mass of the host star. If it is greater than 0.002, this may indicate that star has no unknown gas giants at the least (but still may have smaller planets of course). This is the upper limit on the mass of the protoplanetary disk.

Each new version of SE have up-to-date exoplanets catalog.

TRAPPIST-1 update:
https://www.nasa.gov/feature/jpl/new-clues-to-trappist-1-planet-compositions-atmospheres

All planets are most likely SE terra class, with a densities range from 3.4 (like Moon) to 5.6 (like Earth). Smallest planets certainly have large amounts of volatiles, probably water or ice.





Edit: the plot from the article is more informative. It shows that only planet e resembles Earth and Venus by composition, others seems to have significant amounts of water, or abnormally small metallic core.