I forgot to mention, it is not necessary to edit existing open tasks in Work one by one to add them to the second project. All tasks within a section can be selected (up to 50 tasks) and collectively added to the second project/section from the pop-up bar that appears at the bottom of the screen. After selecting the multiple tasks, click on the clipboard icon Edit project or section and then select Work Filtered and the same section from the drop-down list.
If this workaround is successful for many use cases, perhaps the ASANA developers can write a script to automate this method to allow people to hide or achieve sections from a simple menu option (?)