I don't have any info about editing subtitles but downloading subtitles for an entire series is pretty easy.
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There are multiple tools to edit subtitles. From the web based https://subtitle-editor.org/ to really powerful software like SubtitleEdit
If you have the opensubtitles plugin set up with an account, you should be able to manually run the "download subtitles" task in the scheduled tasks, and this will search for and auto-download subtitles for your entire library. That's the best way I've found, can't speak to editing subtitles that are downloaded. What kind of editing are you trying to do?
Humm, thanks! Never new you could scheduled it. well, there are some series that doesn't have subs on my native language, so I was thinking in using the english ones to generate the correct subs, like using some automated translation tool and later revising it.
Depending the format... .ass
files can be edited by aegisub mostly used by fansubbers in the anime world.