As for now, there is no an API command that you can use for dynamic creation of a custom dictionary or adding new words to it. Such wordlists should be created manually.
If you are using the Cloud version, you can create a custom dictionary from your account on our website. Refer to Configuring cloud custom dictionary guide to learn how to create and manage dictionaries for the Cloud version.
The holders of the Server solution needs to follow Company custom dictionary guide.
