But how can I use an icon on a button? An arrow to go back for example.
At the moment the way to do this would be by uploading an image to the button.
For simple symbols (like a back arrow) you could also always just use Unicode characters like this one:
There are libraries of free icons to download, like this one: https://icons8.com/
material.io is one as well
you cant set the icon size you want. trying to make smaller looks like icon is crop