I (used to) use simonsaysai.com to generate subtitles and they had the functionality to input specialized vocabulary, so I suppose it's possible in some sense but I don't know how it would work with Whisper, something to ask on their Github if nobody else has yet I suppose.

But, for me, the English model works really well. Using the 'large' model works about perfectly for me, I can't think of anything I thought the large model got too badly wrong, is that the model you tried?