I could only find something called [VEAML][2] so far.
[1]: https://gist.github.com/johnloy/27dd124ad40e210e91c70dd1c24ac8c8 [2]: https://david.quotient.space/veaml/
QuickTime used to support it, but I don’t think it’s well supported nowadays. If it did, writing a transpiler from something more Markdown-like to SMIl might be an option.
[2] http://avisynth.nl/index.php/Main_Page
[3] https://github.com/AviSynth/AviSynthPlus/
[6] http://forum.doom9.org/showthread.php?t=153248
and from there on an endless deep dive into almost bitrotten software, which nonetheless refuses to die, because the concepts are viable, and liked by many.
Also: [7] http://www.vapoursynth.com/ and
[8] https://github.com/vapoursynth/vapoursynth
and recursing deep dive into