Nova Floating Button is a free module. It adds a floating button on your pages. You can configure the button parameters. There are four parameters can be set from the module settings. You can set the link as the url that the address of page to be opened when the button is clicked. You can change the icon of the button. And you can set width and heihgt of the button.

https://youtu.be/gpbRlOyVBAQ

https://github.com/bulentbaday/nova_floating_button