Neither Snagit for Windows or Mac allows for the specification of frame rate. Since we do real time encoding (meaning there is no delay or rendering time after stopping the recording) there is a limit to how high it can go.
The algorithm targets a sweet spot based on the activity and tries to maximize quality. We peek at around 15 fps, but depending on the computer, action on the screen, recording dimensions, etc., you might see lower frame rates.
Can you tell us more about why you want to set the frame rate? Do you want it lower than 15? I think we've tried to keep it as simple as possible with this default, but we'd love to learn more.
Thanks for posting!