The method used for managing entities for Goole Assistant (and Alexa, though I haven’t tried) is extremely cumbersome.
The user is presented with a list of available entities, but there’s no way to filter by text, type or location. This makes it very hard to work with, especially on the mobile apps.
My suggestion would be to utilize the same same method for searching and filtering as is available in automations/scenes/scripts.
An additional way to massively streamline this for the user would be a switch for exposing/removing the entity in the entity settings popup itself.