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

Button size depends on size of the menu icon within button. On Button Tab find Icon size setting.

Disabling button for mobile devices

On 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

On Button Tab switch Button type to Custom Icon. Guide for icon uploading

Using custom trigger

Check this guide.