The only working workaround I found has been provided in another thread
Re: Retrieve job-level parameters in Python - Databricks Community - 44720

I will repost it here (thanks @julio_resende )

You need to push down your parameters to a task level. Eg:

1. Create a job level parameter called "my_param"
2. Make a reference to his job parameter in the task level parameters box. Eg:
   
   ["--my_param","{{job.parameters.my_param}}"]
3. Read the task level parameter using argparser in your .py file