Layout shifter allows you to shift between different layouts (Desktop, Tablet, Phone) by resizing the browser. It gives you the experience of having a responsive design simply by changing the layouts that are already in your design.
HOW DOES IT WORK?
When there is a page with a same name in all the layouts (Desktop, Tablet, Phone), if you place the widget in all those pages, you can resize the page and the browsers shifts between the layouts like it is a responsive website.
You can place the widget on the Master pages, in all the layouts, so it applies to all the pages in the project (if you have the same site map on Desktop, Tablet and Phone)
WHAT IS THIS WIDGET FOR?
At the Desktop layout, resize the browser. As soon as you reach the breakpoint the tablet layout shows up. Then again, when you resize the page, the Phone layout shows up. This way you can simulate a responsive site by using the Tablet and phone layouts in your Muse project.