Hi Rafael,
Thanks for contacting Syncfusion support.
In TreeGrid, the Horizontal scroll bar appears and disappears depending on the width of TreeGrid, by default. You don’t have to enable or disable it. Here, we have prepared a sample with 8 columns and TreeGrid width as “450px”. You can find the sample under the following location.
Sample: http://www.syncfusion.com/downloads/support/forum/120225/ze/HorizontalScrollBar756921197
If still, you face any trouble to render the Horizontal scroll bar, please get back to us by modifying this sample.
Regards,
Mahalakshmi K.