After having deleted a project by accident, I came to regret not having a trashcan.
Confirmation dialogs only go this far... I selected the wrong project because it moved to the top of the list after I clicked on "Tinker this" instead of the "Actions" gear (and btw, sorting projects by modification date is kind of annoying: let me choose between name, creation date, modification date and group by project yes/no).
Behind the scene trashcan functionality could be implemented by just moving the design to a hidden project. Then add an "empty trashcan" routine to delete everything in that project.