Found a neat wee guide on Reddit for this – thanks to FFS!
Press Windows_logo_key + R to pop-up the Run command box and then type %localappdata%\qBittorrent and hit enter. You’ll get a folder and minimize it.
Again repeat the same process and this time type %appdata%\qBittorrent instead of %localappdata%\qBittorrent. You got another folder and now you have two separate qBittorrent folders.
Select and copy everything from the newly two opened folders and paste them to other two folders (1 for %localappdata%\qBittorrent and 1 for %appdata%\qBittorrent) and save the folders in a safe directory.
Restore Process
After installing, close qBittorrent by pressing Ctrl+Q.
Follow the previous steps again to open %localappdata%\qBittorrent folder.
Delete everything from that folder and copy everything from the backup we kept earlier for that folder.
Repeat same process for %appdata%\qbittorrent folder too.
Open qBittorrent and it’ll detect all your torrents