Got it. To make it stay visible we can use adjust. This option determines the kind of viewport positioning that takes place. If we put adjust: {method: none shift} - then the tooltop, when is getting out of visible, will not move horizontally (none) and move vertically (shift).
For more option read the manual. http://qtip2.com/plugins#viewport
position: {
at: 'center left',
my: 'right center',
effect: false,
viewport: $('.mainPanel'),
adjust: {
method: 'none shift'
}
},