hello,
about select control,I read you office document, it is a drop-down list box,but it just one level to select,I have a demand,could you provide multi-level to select like tree-select,like that 
this.demand is very important for my project,so I hope you help me to achieve it! thank you!
Hello @fengshichao ,
Unfortunately, the gantt chart doesn’t have the built-in tree-select control, but you can implement it with the Custom inline editor functionality as described by the following link:
https://docs.dhtmlx.com/gantt/desktop__inline_editing.html#custominlineeditor
In this case, you will have to return some tree-structure HTML elements from the show property. Unfortunately, I can’t provide you any ready demo that realizes such functionality.