Big(ish) news - there is now a beta version of the CapMaker available for the desktop! That's right, no browser needed! Binaries are available for 64-bit Windows, Linux (I
think only 64-bit) and macOS.
https://github.com/eriqjaffe/capmaker/
Note that most of the image processing tools require a working installation of
ImageMagick. Installation instructions for ImageMagick vary depending on your operating system - they have documentation available on how to install it for your operating system. Fair warning, installing ImageMagick on macOS is a bit of a pain in the ass.
Feel free to take it for a spin. As mentioned above, this is a
beta version so some things may not look quite right or may not function as you might expect. Let me know here and I may or may not try fixing it.