The drag and drop row moving (https://doc.daypilot.org/scheduler/row-moving/) allows moving one row at a time. It will move the selected row, including all children.
You can also change the resources tree using the API - just modify the hierarchy using "resources" property and call update().
If you have a flat list of resources you can easily use Array.prototoype.splice() to remove the row from the old location:
var row = dp.rows.find("A");
var index = dp.resources.indexOf(row.data);
dp.resources.splice(index, 1);
And insert it at the new location:
var insertBeforeRow = dp.rows.find("C");
var index = dp.resources.indexOf(insertBeforeRow.data);
dp.resources.splice(index, 0, row.data);
For complex tree structures, it might be easier to make the change on the server side and reload all the resource data.
See also: https://forums.daypilot.org/Topic.aspx/4304/move-resoources