Hi there!

Thanks for contacting us.

You will find it as a button in your modules list.

However, you can use the following code to get rid of the whole menu column:

#sp-menu {
    display: none;
}

It will remove both the button and the offcanvas for you!

Note: Path towards custom CSS(Joomla 3): Extensions>Templates>Styles> Click on your current default template name then choose Template Options. Then find custom CSS within the custom code.

Best Regards