Actually, Camtasia uses the GPU for timeline playback in the editor and that's about it. I have a pretty good Nvidia GPU and it doesn't get used in the rendering process. I'm not sure what you mean when you say you can force Camtasia to use it through the Nvidia control panel? I don't see how that's possible? The control panel only has settings for display management. See image.If you see something I'm missing, let me know.
While I'm processing on Intel Core i7, I was wondering the same thing for the last few months. I've just updated to Camtasia 2018 and it would appears that Camtasia 2018 is taking full advantage of my Nvidia Geforce GTX 1050 GPU. In the past all project rendering was done by the CPU. Glad to see the update, a lot of folks asking for such support.