I’d like to ‘automate’ my BOM generation scripts with the contents of some user defined variables, like:
does anyone know if it is possible?
If yes, can someone point me to some code example?
Have you tried using ${variable_name} ?
no, but i can ! (not the brightest coder of the lot here talking, but i can proficiently copy paste pre-written code 
)
I’m pretty much in the same position . . . I’ve only used my own variables in symbol fields, not in any scripts.
I’m sure someone will be along with more info soon 
The KiCad project file is in JSON format. It is easy to open the file in Python in order to search for the variable name and contents.