Media Mix Modeling MMM - saturation function & ADSTOCK function

Does anyone know a saturation function to add to the Media Mix Modeling MMM that allows me to identify the saturation point of advertising expenses, and how to implement it?

I found the ADBUDG function relevant for saturation, however I don’t know when to add it to the MMM model, if before or after the ADSTOCK function, and I don’t know if it is possible to add the two functions (ADSTOCK and the ADBUDG saturation function)

Additionally, I thank you if you have any other ideas for a saturation function and how to implement it, particularly when I have the need to implement the ADSTOCK function.
Or if there is some function that serves to take into account the adstock and saturation effects at the same time?

Thank you all for your answers, they will be of great use to me.