It's not possible to relink already made folder structures automatically with qBittorrent, Deluge and others. Below is a workaround.
Qbittorrent is a torrent manager that sorts torrents in categories inside of it's GUI. This has one major implication, all files should be sorted inside of the torrent program and have a flat hierarchy inside the filesystem on the operating system for the easiest relinking process.
Sorting and managing files inside of a torrent program and not inside of the OS file system might seem counter intuitive, it does to me, it should be possible for torrent programs to adapt to our already created folder structures inside our file systems and not force us to use their GUI's for sorting files.
I would be more happy with manging my torrents inside of the torrent program if the torrent program allowed for nesting folders, like any OS does, but qBittorrent does not have this feature enabled.
My solution for relinking old torrents with a new folder structure is to use a flat hierarchy and manage my files inside of the torrent-programs GUI.
While it's unadvised to sort things in the filesystem (for the sake of the relinking torrent process, it' makes relinking all files very slow) of the OS it's certainly possible to do so. To speed up the relinking process of torrents and their file paths in the filesystem when sorting files use the built-in search function of the torrent program to locate multiple files under the same name and then relink multiple files at once by using
set folder &
Likewise, you can improve the speed at which you find folders when navigating in the OS file-system by using an application like Listary and it's built in search function to quickly navigate to the torrents destination folders.
My wishlist for all torrent programs is that they create an automatic relinker for those times when organizing an older folder structure becomes necessary. There are threads about an automatic relinker in qBittorrent, you can see them here, unfortunately it's not yet been implemented.
Know a torrent that automatically relinks folders with torrents? Let me know in the comments below.
Hope this helps.