Suggested by StewartLikesLingQ on this post:
"It would be even better if LingQ had it's own plugin like language reactor allowing us to LingQ/Mark Known Words on Youtube/Netflix subtitles without needing to import them into LingQ which would save a lot of time. For now I have to use LingQ side by side and it's a hassle or else I just have to read through the subs on LingQ first and then watch the video with Language Reactor after or vice versa."