If you are using the Cloud version of the product, the number of dictionaries per subscription is limited to 5*N of the languages supported. Thus, for the standard subscription with 17 languages, you can create up to 85 dictionaries.
Starting WebSpellChecker on-premise/server version 5.23.0.0 the number of custom dictionaries was limited to up to 100 wordlists. If you are a holder of the previous version of the software, there is no limit on the number of dictionaries if you are using the on-premise solution.
