The total number of Chinese characters from past to present remains unknowable because new ones are developed all the time – for instance, brands may create new characters when none of the existing ones allow for the intended meaning. Chinese characters are theoretically an open set and anyone can create new characters, though such inventions are rarely included in official character sets. The number of entries in major Chinese dictionaries is the best means of estimating the historical growth of character inventory.
How are these documented?
such inventions are rarely included in official character sets