Under macOS Mojave, I have System Preferences > Dock > Double-click a window's title bar to zoom turned on, but Caprine doesn't honor it.
I'm surprised, in that I haven't run into any other app that doesn't. Perhaps it needs to be explicitly accommodated because Caprine has some sort of "roll your own" title bar/upper frame, to accommodate the splitter? Just a guess--I haven't examined the code, and I'm not very familiar with macOS development.
For the record, Option-clicking the Zoom (green) button in the Caprine title bar does work, accomplishing the same thing that double-clicking the title bar should.
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