As far as I know, supporting extended storage cards means that the electronic dictionary can insert an SD card to expand the capacity of the dictionary itself to store text, such as TXT files, and display the text documents you have edited through the dictionary. If the text format is not supported by the dictionary, it will not be displayed.

It is not impossible to edit the dictionary yourself and store it in TXT format, but it may not be more authoritative, correct, and detailed than the content contained in the dictionary itself. Generally, some conversations, short articles, famous quotes, or electronic novels are downloaded to increase entertainment.

It is impossible to update, replace, or expand the existing vocabulary through downloading. Otherwise, Casio wouldn't be able to make money, and there would be no need to produce so many different models of dictionaries.