Dependencies were added as a field in CSV files exported from projects. Discussion on that here.
However, if that CSV is then imported into another Asana project- the tasks do not link correctly and instead additional columns are added into the project which simply list the names of tasks that a particular task is dependent on. If a task is selected, the dependencies section of the task information is blank.
Suggestion is that tasks that are linked in a project that is exported to csv and then that csv is imported into another project- the links remain as per the initial project.