I've been using the Markup in Preview since they went system-wide in macOS Mojave. (Today I learned that Markup debuted as an extension in Mac OS X 10.10 Yosemite. [0])
This comment and its children sent me on a spelunking mission and the treasures I found. Markup has a Loupe tool and Speech Bubbles.!
Such features are many, various, and somewhat obscure, akin to Easter Eggs. (Both undiscoverable and handy to know.)
[0] https://tidbits.com/2018/11/19/macos-hidden-treasures-the-ma...