Session Timeout - can I modify text and behaviour?

The default Session timeout message does make sense - how are you supposed to save your work?
I dont understand what benifit interacting with the timout notification brings - you are forced to close the notification by clicking on it or pressing escape to continue .
I would like to be able to change the text to something more sensible which I can do in a css hack but would like to do it properly and I would like to be able to use the mouse to login from the menu rather than having to click on the message or pressing escape.
Can ysomeone tell me how to do this please

Yes you can change the messages. Check documentation for customized system messages here:

But documentation seems to be little wrong, since in Vaadin 8 (nor in 7) there is no application class anymire. Setting and getting system messages is done via VaadinSerlvet.getService()… See documentation for VaadinServletService and VaadinService.

Changing behavior is more tricky. You need to research the code and check if the method taking care of this can be overriden etc.