Floating or fixed
To change button behaviour from floating to fixed head over
Button Tab and turn on Button fixed on page setting.
Button size depends on size of the menu icon within button. On
Button Tab find Icon size setting.
Disabling button for mobile devices
Button Tab enable Navbar for mobiles setting. To disable menu on mobiles completely head over 🍔
Main tab and make changes under General Display Rules.
Using custom icon/image for menu button
Button Tab switch Button type to Custom Icon. Guide for icon uploading
Using custom trigger
Check this guide.