As far as I understand it, effects are handled basically the same way in c2 and c3. The only additional effect parameters you can add are numbers. You can’t pass additional textures to construct effects at this time.
However it is possible to do it from a plugin’s drawgl function. Tell construct’s renderer to finish drawing, and then do any custom webgl you like. The pro of this is you can do anything. The cons are you have to deal with a fair amount of webgl and you’ll have to change the webgl state back when you’re done. The closest example I have is here, but it touches on more things than you’ll need.
construct.net/en/forum/construct-3/how-do-i-8/how-do-i-get-this-example-to-w-140574
It’s fairly low level but could be a useful starting point.
Either way your effect is pretty cool.