I think I found a bug in the treetimeline-extension.
It concerns the name of the section, which normally is “section_id”. But in my project I use another section-name.
I found the bug, because I was unable to drag events in a timeline-view with “render” set to “tree”.
The bug is in ext_treetimeline.js in the “onBeforeEventChanged”-handler on line 84, where it explicitly wants “section_id”:
var section = scheduler.getSection(event_object.section_id);
I looked around a bit and found that 3 lines further it is used correctly:
event_object[scheduler.matrix[scheduler._mode].y_property] = section_id_before;
So I changed the erroneous line to:
var section = scheduler.getSection(event_object[scheduler.matrix[scheduler._mode].y_property]);
That fixed the problem.
I hope that helped.