your data
all of it lives in this browser, on this device. clear your storage and it is gone, so export it somewhere occasionally. that is the whole warning.
what is in here
events0things tracked0
export
one json file, everything in it, readable by a human.
import
merges into what is already here rather than replacing it. importing the same file twice changes nothing, and importing a second device's file gets you both histories.
delete
everything, permanently, with no copy kept anywhere. export first.