Thank you for contacting Syncfusion support.
Currently we don't have any option to display ellipsis when tree node exceeds the boundary and display the tooltip while hover on ellipsis. We have considered this as feature request and have logged a report on “Support for display ellipsis when tree node text exceeds the boundary”. The feature can be tracked through our feedback portal below.
Please cast your vote to make it count. We will prioritize the features every release based on the demands. If you have any more specification/suggestions to the feature request, you can add it as a comment in the portal.