Hello again,
Just to let you all know that I found a solution using Python. I've created an notebook (ran from ArcGIS Pro) where i create an scatter plot image using the matplotlib library, update an image item in ArcGIS Online with it, and then consume the resulting image in an embeded content widget in an ArcGIS Dashboard.
In case someone will need to do this implementation in the future...
Regards,
António Marques