If you are moving between spaces there are two tools to do this https://asana.kothar.net/ which has been around for a long time and as I understand is in the process of working on version 2. In full disclosure I am the owner of Sendana Add which will also move between spaces. This is covered on the post Sendana Tools-Sendana Add- A Novel Way to Add and/or Transfer Projects and Tasks In Mass - #9 by James_Carl
@Bastien_Siebman in regards to the differences, we developed Sendana add to have many option switches as well as the distinct difference to copy tasks or projects between spaces or within a space. Complete instructions on its use and capabilities are attached. Both can only do what the API allows. I believe we have encompassed everything we can including sections, dependencies and documentation if custom fields are involved. We also allow multiple copies to be processed at once. Kothar has been a valuable resource for years and one can actually try both if they want to know the differences. I really can’t speak to that.
Sendana Add Instructions.pdf (193.3 KB)