When the Camtasia Mac update came out a few years ago, I was intrigued by the new sketch motion callouts included in the media. Essentially, they're little animations of circles, squares, squiggles, and arrows to spruce up my videos. They were cool, but I quickly wanted the ability to create my own custom callout for my videos.
Using some Camtasia trickery, you can create custom animations. I tried it and made a short proof of concept video to make sure it worked. Rather than typing the whole thing out, I made a short video (4:30) on the process I used. You can see it below or watch it on YouTube. After the video, I've got some other tips on how to manage the custom callouts you make.
If I were going to do this frequently, I would make a little library of callouts to import. You can't add media to the library in Camtasia Mac (but you can in Camtasia Studio on Windows), but you can make your own library of callouts. Go through the process I outlined above and then export your callout as an mp4. Save it in a folder on your computer and then import the callouts when you need them in later projects. They're so small, your videos won't have a noticeable difference in file size.
It is a little convoluted, and will take some time, but after you get the process down, you should be on your way to making your own custom callouts. If you have one you want to share, put a link in the comments below.