Firefox 57 …
I'm aware that Save Image in Folder and Save Link in Folder are no longer compatible with the latest Firefox releases.
These extensions are based on Mozilla's XUL- and XPCOM-APIs, which are now obsolete and no longer supported.
Bringing the extensions back to life would require a complete rewrite using WebExtensions.
Unfortunately at the moment I can't give you any details on when (or even if) I will be able to accomplish this task.
I will look into it if time permits.
Thanks for your patience!