I wonder if there is a widget that allows me to showcase how my pages look in different screens. Something like this:
It´s called responsive design and is manageable in muse. Widgets are part of muse for accordions, state buttons, menus, galleries and so on. There are also quite a few 3rd party widgets out there.
You may start to watch some tutorials first like here: Muse-Tutorials .
In the near future you may test it for 30 days or if you are already subscribed to adobe creative cloud, go ahead.
You misunderstand my question. I'm already using Adobe Mouse.
I wonder if there is a widget that allows me to present the pages I have created in adobe muse in the same way as the image below.
There´s no widget for this, as far as I experienced. You may have to do this with some mockups and fill in your images as needed.