Why I can't see the changes made in Customize section?

Chatwee saves every user's personal settings into the browser via cookie. That's why you should clear your cache and cookies related to Chatwee widget to see the new settings properly.

You can follow the manuals below:

Deleting Cookies in Firefox

https://support.mozilla.org/en-US/kb/delete-cookies-remove-info-websites-stored

Deleting Cookies in Chrome

https://support.google.com/chrome/answer/95647?hl=en