I'm sorry this has caused a problem for you. The default download directory can be changed in about:preferences -> General -> Files And Applications -> Downloads -> Save files to . It is technically possible for the extension to set the default download directory and I am going to look into how I can implement this. However it seems most likely this would need to be configured in the add-on options tab.

EDIT: Unfortunately it is not possible with the current webExtension API for me to change the default download to anywhere outside of the default download folder set in preferences. As stated in the docs "Absolute paths, empty paths, and paths containing back-references (../) will cause an error.". As such I believe it is futile for me to add any sort of download path remembering feature as it would only work for folders inside the default download folder.

If you wish to read more about this: https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/API/downloads/download