wbeditentity has two modes: per default, and data supplied is added to the entity. If the "clear" flag is set, the current entity is replaced with the new data instead.

The clear/replace mode is semantically tricky, see T171483. We want to know how often it is used, so we can decide how much time we want to invest into making it work nicely, or whether we can remove it completely.

Note: this is complementary to T172100: get list of users of API module wbeditentity with clear flag which is about analyzing HTTP logs.