Add ggplot2 layer to clinical data

[Sheneice.c]

Hi, I am having several questions on editing my clinical data for waterfall plot

1. I would like to group my clinical data legend according it's category, eg: age group and population.
   Even though the plot function is specified on package under Bioconductor but the arguments, clinLayer stated: Valid ggplot2 layer to be added to the clinical sub-plot so I would take it as finding an answer from those who are familiar with ggplot2 function instead? griffithlab/GenVisR source: R/deprecated.R

   This is a picture of my current plot and all the legend labels are clustered together so I would like to separate all of them with the groupings like Age, Disease status, vital status, and population.

   

   I am not familiar what does it meant by a valid ggplot2 layer. I didn't post a reprex() as the data is not fully available online and I only interested in editing my clinical data by creating a valid ggplot2 layer.

2. Besides how do i create a line to separate population as the plot shown in the link? Introduction to transition/transverion plots | Griffith Lab I tried to set the xintercept by variables in ClinData but it creates error: Error in UseMethod("rescale") :
   no applicable method for 'rescale' applied to an object of class "factor" . Is there any other online tutorial that is easier for me to apply?

Welcome any suggestions and comments! Thank you in advanced!