Best practices for lengthy forms

I am designing a form(non-linear) where we have 3 categories and each category can hold 100+ fields. Application will be used by skilled technical users and the fields would be product configuration.

My take is-

  1. Create logical segregation of fields
  2. Put categories in the left panel(cannot use stepper as user can jump in any section( fill the fields, save and leave the page. They don't need to fill the complete form in one go. It is similar to the various social media application where users complete their whenever they need 3.They can again come back and fill any section they want( I will put % of completion against each section)

My problem is - I am not sure if the solution will work or not

Is there any similar application and problem you have solved and seen.