How to best improve information density for long, complex forms?

How to layout long, complex forms such that the largest possible number of fields is visible on the page, but legibility is maintained?

I am re-designing an enterprise web app where there are a total of 30x fields across 5 sections when creating a quote, and where an extra 10-20x fields get added depending on the state of the quote.

The client has expressed a strong preference for seeing as many form fields as possible within each screen without having to scroll, (this request seems sensible but I am yet to test)

This is what the form looks like:

enter image description here

My initial attempt was to introduce clear-er hierarchy and group the inputs into further sub-sections:

enter image description here

But I think the UX could be further improved by flowing the content within each tab vertically (and using the sidebar to present a summary) instead of horizontally + vertically.

Are there any other patterns that could be suitable here ?

What other ways are there of keeping a large number of form fields visible ?

Tags: