If/untill Ratanak fixes the issue with magnets not getting there labels resolved automatically(when matching by filename), then a workaround is to make use of a magnet2torrent converter. There's a simple bash shell-script posted many places for use by rtorrent, but the produced torrents isn't compatible with deluge(not bencoded?). There's also online converters, but that goes against what we're after here in the first-place imho. i.e. automation(+ didn't worked very good as just added a new tracker!), but I found a nicely working python implementation here: https://github.com/danfolkes/Magnet2Torrent
Single small file, only needing python and libtorrent python bindings, so nothing extra to install. Download, chmod +x, place under PATH somewhere, and whip-up a small shell-script which you set to get invoked by your browser when selecting a magnet.
Magnet_To_Torrent2.py $1 ~/Downloads/filename.torrent
deluged; sleep 2; deluge-console add ~/Downloads/filename.torrent
Firefox lets you choose a shell-script as handler e.g. for magnets, but chromium uses xdg-open, so e.g. make a deluge.desktop file and place under: '~/.local/share/applications'.
(I have set it to handle both torrents and magnets in above example(in 'MimeType' line) as my deluge-run shell-script handles everything for me and e.g. stops daemon when downloads finish, deletes torrents and plays a notification-sound etc, but you can change that to only magnets of-course. Also, if you have a daemon running always and a directory monitored, then I guess you could just use Magnet_To_Torrent2.py directly in above desktop file and ditch using a seperate shell-script.)
Edit: There's also a fork of magnet2torrent with a few extra options, like auto-opening the produced torrent with default torrent app, and not needing to define output-name which just gets taken from inside the magnet, and some extra overwrite or not options: https://github.com/LordAro/Magnet2Torrent