execute a script will, execute any code inside of the code block.
You need to make sure you have the shader Toolkit script added as a definition script for the shader functions to work.
The Toolkit script provides the initial setup & defines the functions & creates a loop that is used to check for when functions have been executed or custom shader scripts (glsl) have been executed in a function or script.
Instead of setting up execute a script actions inside of key inputs or actions try using the console instead. Just hit the TAB key to open the console.
then in console type: exec
& then after exec you type your script & press enter.
quick example:
exec shaderContrast(1.1, 3000)