show two slides with a button
Possible Answers to Your Question:
This is only possible if you are developing your own extension |(the stock slider cannot be customized to this level with DevKit alone)
Slider behavior triggered by the user is up to you in how you develop your widget and in the supporting JS you add. If you are thinking of a button that the user clicks to change the slide view from one to two per panel, you will have to pass that option to swiper using Ajax so it can adjust its width (as well you would need to add a new class that loads the correct CSS to size the slides). If you are looking for a slider option that allows users to choose between normal and two slides per panel, you would have the same requirements with the difference being that one is an option in the widget array and the other is just a button with a JS trigger.
For help with customizing or building swiper js functions, please visit their community forum here: