I'm not so sure about the hotkey feature but i can give it some thought.

Addons should not and in fact cannot download files to anywhere outside the browser's download directory. This addon does have a subfolder feature but firefox currently doesn't support it yet.

Also, you and everyone else, please stop using AMO "reviews" to request features. These reviews aren't a means of communication, and developing new features or fixing bugs requires communication. I've put email and support site links on the main page for a reason, please use them.

That already exists in your browser: "Save image as..." or "Save link as..."

Please don't make AMO reviews to request features or talk about bugs. Send me an email or post an issue on gitlab. The relevant links are on the addon's main page here.

You don't. Downloads will and should go into the user's downloads folder. Please don't make reviews just to ask a question, that's what an issue tracker is for ("support site").

Don't worry about code maintenance, that's my job. The disabled features are there because they carried over from the original addon and the chrome version, and I expect them to be possible in the new firefox soon.