Firefox Quantum (57.0 …)
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!