There is no logout function within Xeno App.
Also it is bugged for me - I cleared data, cleared cache, uninstalled app, rebooted phone, installed Xeno > still logged into my account.
Use case: I have two Xeno accounts as I own one for my own store and then am part of another Xeno team to assist with chats on their store. Right now I need two phones to handle chats because I can't log out of my account, or I need to use a clone app so that I can run two instances of the same app.