App for streaming/screenshare

Hi, I plan to start presenting the Cards of Truth (and vedic/tropical astrology to some degree) in Spanish. I´m looking for a software that allows me to share just a small part of the screen, since the boxes in Kala are small, and at the same time has a more broadcasting-like look than Zoom; something like Streamyard. Does anyone by chance no about the existense of such a program, or a way around the problem (like a program that captures part of the screen and is possible to show in Streamyard)? Using two screens is not an option since I travel a lot.

Or if you know someone that might have a solution.

Best regards

Mattias