Hi Elizabeth,
Not sure if you are still having trouble but I presume you are trying to indent the set of tasks. You will usually find Workfront refusing to do that if some of the selected tasks are not at the same level. You mentioned you have a large number of tasks so I would check carefully and make sure you select only tasks which are already at the same level.
One other tip is that - depending on what you are doing - it is often easier to create a new project and do the editing there before converting it into a template.
Regards, David
