Hi @emeffinsteve, welcome to the Supernotes Community! 
There is indeed a hard limit for cards at 24,000 characters. Supernotes is designed for short-form content (hence the card format), and we’ve done this intentionally so your Supernotes is both fast to input, search and connect together especially compared to other platforms.
Why not split up your transcript into multiple sections? And then have a parent card summarising the transcripts? This will make it a lot easier to navigate and read, especially on mobile devices.