Sub sections in sections of form progress bar?

Currently working on designing a form for tuning machine learning models. The form currently has a progress bar on top with the sections divided. We were recategorizing all the sections and realized that there are multiple sections that can be grouped together. However, each section is too long and dense to be shown as one and must be separated. Does anyone have ideas as to how to show grouped sections as separate yet a part of the same concept when using a top progress bar? Let me know if this is not clear.