Tree Item with subtitle

I want to implement a tree structure, where each tree item can have a subtitle which is directly displayed below the “title”.
To achieve this I have set HtmlContentAllowed to true and then tried to achive it by using html code for the item caption. Currently I am facing a problem, that the arrow icon of the tree item is displayed at the same level as the subtitle, but I want to display it next to the title. Please have a look at the attachment.
What do I have to change in the css that the arrow icon will be displayed next to the title?

Thank you for your help!