I wanted to add a tag like
black-hole-merger to How do we know that supermassive black holes can gain mass by means other than merging with other supermassive black holes? but couldn't find anything close.
Considering the number of gravitational wave questions we have and the ever-expanding observational capabilities of current and future devices, mergers are going to be regularly posted questions.
merging-events or something similar be a good idea? Should it be specific to a pair of black holes? What about a black hole/neutron star or two neutron star merger?