progress bar – User Experience for non linear steps

We are in process of creating guided user experience for simplifying onboarding on multiple processes, services and teams. End User will be tech users only.

Our web application will create multiple steps (it could be more than 7-8 to 20 steps). Some steps are independent while others are dependent on previous steps.
Steps can be grouped like 3-4 steps per group.

If I use Progress Tracker with 20 steps I am facing 2 problems.

  1. So many steps will create confusion.
  2. How can I inform user that some steps are independent can be done in parallel.

Consider I am making a group of 3-4 steps then if I use Horizontal progress tracker per group and vertical steps within group, then how can I give clear view to user about steps which can be executed in parallel ?

Is there any better intuitive UX by which we can inform users that these steps can be done in parallel and some steps can be done only after completion of previous ones ? Also how we can show overall progress ?