...
To drag & drop tickets on Gantt, users need to turn off all Quick filters and turn on view setting Show completed tickets → At this point, you can drag tickets on Gantt
...
...
More Advanced Features in Gantt / Timeline
Save your Customized Views
Save your customized views in the Gantt chart , enabling you to retain your preferred layouts and settings for future use, ensuring fostering a more personalized and efficient workflow.
To save your view, click on the View Options menu in the top-right corner of the Gantt/Timeline → click on 
icon → Name the View → Confirm by clicking the Save button.
...