Open your webmail in a browser and create any new folders / labels needed. Then, in the Thunderbird app... 1. Open the account list. 2. Select account. 3. Tap manage folders. 4. Tap 3 dot menu. 5. Tap refresh folder list. There's no method currently to create folders directly within the app. You can vote for the feature using the Mozilla Connect link below. https://connect.mozilla.org/t5/ideas/add-the-ability-to-create-imap-folders/idi-p/72777