The Archive function moves completed tasks individually based on dates. It does NOT move entire projects or folders. That plays holy havoc with my ability to keep track of every detail on a project until it is completely completed. For this reason, I absolutely avoid using automatic Archive at all. Instead, I archive manually.
* --> File : Open Archive … This opens your archive file.
* Go to your active file and COPY the folder or project that you want to remove.
* Go to the archive file and PASTE that folder or project in place (caveat below).
* Go back to the active file and DELECT the folder or project that you wanted to remove.
CAVEAT: When you paste a folder or project manually, you may see duplicate folders appear. This happens when your pasted folder or project is in a sub-nested set of folders. The manual mood to copy + paste (or drag + drop) projects or folders has a serious bug in this regard [and YES IT HAS BEEN REPORTED many many months ago].
In summary …
The automatic Archive function gives you control only on the date before which TASKS should be archived, and the manual archive method to remove folders or projects can become tedious and has an annoying bug.