How to hide environment variables when putting configuration file in plugin folder

ducnv_resolve Greetings

As it is all happening on front-end side, there are not much way of hiding the token, and in any case it will be possible to see it on a debugger on Mapbox related methods.
What you can try is to whitelist Sisense URL for that token to make it non-usable outside Sisense and therefore there will be no need to hide it. 
Please check the article and let me know if you have any questions.
https://docs.mapbox.com/accounts/guides/tokens/#:~:text=You%20can%20make%20your%20access,from%20the%20URLs%20you%20specify

Best regards,