If a torrent file includes several files to download (e.g. a multi-episode film or TV series), how can I set only selected files to download? For example, to download several episodes rather than the whole series.
Is there such a possibility in the embedded Transmission torrent client?
Yes, the interface of the built-in Transmission torrent client has such a feature. For illustration, let's see a screenshot of where the file selection is located.
The arrows mark where to click and what to select when downloading files. Then set the priority to 'High' for the files you want to download and 'Low' for those you don't want to download.
Alternatively, you can use the Transmission Remote app, which conveniently selects the files you want to download to your USB drive. For example:
You can also similarly use the rTorrent client.