In Gantt , undo and redo is not working on groupby resources

In Gantt , undo and redo is not working after using groupby function based on resources

Hello,
Thank you for letting us know about that issue.
I was able to reproduce it in the following snippet:
https://snippet.dhtmlx.com/ynki4r6x

It seems that the Undo and Redo stacks are reset after grouping, so if you do something, then group tasks, you won’t be able to Undo and Redo the changes.

If I do something in the grouped mode, the Undo extension seems to be working, though with the vertical reorder, a task will always move to the top group after Undo, and we are aware of that issue.

The dev team will fix the bugs with the Undo extension in the future, but I cannot give you any ETA.