To create a split button add class .dropdown-toggle-split with your dropdown toggle class And to add divider between dropdown item use class .dropdown-divider

To create a dropdown with split button use .btn-outline- with your dropdown toggle

To create dropdown with you can use .btn-lg for large and .btn-sm for Small with your .btn class

You can use drop from different direction to use drop from bottom end use .dropdown-menu-end with your .dropdown-menu. For drop up use .dropup as a wrapper. For drop end use .dropend as wrapper. For drop start use .dropstart as a wrapper.

To create a dropdown with groups you can use .dropdown-header for the header of groups and for separation of group you can use .dropdown-divider.

To create a dropdown with icons use class .dropdown-icon-wrapper with your dropdown and you class class .dropdown-icon with the default <i> tag.