No there isn't. Camtasia 7 doesn't have the remove a color effect which is required. That was not added to Camtasia until version 8.
Theres a program called Hit Film Express. https://fxhome.com/hitfilm-express The 100% free version has a Color Difference Key filter that you can use for as a chroma key filter. It's not as powerful as a true chroma key filter.But it works pretty good.
In the image below is an example of me using the software and keyed out with an image behind me.
It does a much better job than the newest version of Camtasia.
You could purchase the actual chroma key filter for $16 if you wanted to. Thats how the program works.There are a lot of things you purchase to upgrade its functionality.
Or you can get a fully functional version with all the features.For another price. https://fxhome.com/
Then produce a video in Hit Film and import it into Camtasia 7. Or Record videos with 7 and edit them with Hit Film.Whatever makes the most sense in the moment.