Hi Andrew,
Thanks for your interest in Syncfusion products. And I apologies for the delayed response.
You can achieve your requirement by using help text of the tree node. On mouse hover it will display the Tree nodes text as below the node. For more information i have included the sample as follows.
[Sample Link]
http://www.syncfusion.com/uploads/redirect.aspx?&team=support&file=TreeViewAdvSample443836212.zipPlease let us know if you need further assistance.
Regards,
Iniyen M.A,