UPDATES: This feature is already added and the issue is already resolved.
Currently, our javascript widget does not support JWT but we are working on updating it.
Meanwhile, we suggest embedding the page that you need directly using an iframe. Below you can find all the different embeddable pages that we support:
https://community.tribe.so/question/5ce6eb59384efb63036c716a/answer/5ceab260b9790226e976bfaf92
You can easily add ?ssoToken=[JWT Token]
at the end of any of the above widgets to single sign-on the user. Please note that our Javascript widget does the exact same thing as well, meaning that its result will be an iframe with the right components selected. Therefore, there would be no difference between generating the iframes manually or using our JavaScript widget.