Hi marco del frate,
Greetings from Syncfusion.
You can achieve this requirement by introducing a new Boolean (CanEdit) property in the custom model and based on its value, restricting the dragging in the NodeDragCompleted, NodeResizingCompleted, ProgressResizing events in Gantt, and canceling the CurrentCellStartEditing event in GanttGrid. Please find the sample from the below link.
Please let us know if you need any further assistance.
Regards,
Vignesh Ramesh.