Just a list of all css functions. Based off of the MDN css reference
All css functions, copy-paste with ease:
["annotation", "attr", "blur", "brightness", "calc", "character-variant", "circle", "contrast", "cubic-bezier", "dir", "drop-shadow", "element", "ellipse", "grayscale", "hsl", "hsla", "hue-rotate", "image", "inset", "invert", "lang", "linear-gradient", "matrix", "matrix3d", "minmax", "not", "nth-child", "nth-last-child", "nth-last-of-type", "nth-of-type", "opacity", "ornaments", "perspective", "polygon", "radial-gradient", "rect", "repeat", "repeating-linear-gradient", "repeating-radial-gradient", "rgb", "rgba", "rotate", "rotatex", "rotatey", "rotatez", "rotate3d", "saturate", "scale", "scalex", "scaley", "scalez", "scale3d", "sepia", "skew", "skewx", "skewy", "steps", "styleset", "stylistic", "swash", "symbols", "translate", "translatex", "translatey", "translatez", "translate3d", "url", "var"]