Words can be added to a dashboard where the Spelling section is available.
To add words to the dashboards dictionary you will need to be on the Spelling section of the dashboard
Under Misspellings by word you will see a purple dictionary icon that can be used to add words to the dictionary
Clicking on this icon will listing all the potential misspelled words, you can then tick which words need to be added to the dictionary.
Once you click on the Add button the list of words to be added will be displayed. A drop-down option will also be available to confirm if the words are to be added to the current dashboard or applied to all the dashboards.
If you do not see the dictionary icon this would mean that you do not have rights to add words to the dictionary