This plugin allows you to split a dropdown into multiple dropdowns based on the level of splitting you want.
Installing this plugin is done following the standard process for itsm plugins, simply clone the git repository or download a release and place it within ITSM plugins folder.
Unzip the plugin archive, set Apache rights and enjoy !
Go to Configuration > Plugins and click on Split dropdown to access the configuration.

The splitting dropdown list is displayed below.

When you add a new enabled splitted dropdown, a preview is displayed for you to test the dropdown split.

Note : a splitted dropdown is updated when you added the same dropdown type.