Welcome, @Dolores_White1,
You can already do this in a couple of ways in Asana.
One way in Timeline or Gantt views; click+drag to lasso multiple tasks, or Ctrl/Cmd+Click multiple tasks, then move any one of them left or right to move them all relatively.
https://forum.asana.com/t/dependencies-in-timeline-gantt-chart/183844/2?u=lpb
Another: See the Asana help:
Auto shifting dates for dependent tasks
Thanks,
Larry