I need to create a rather complex wizard which shows the progress of 3 main steps, and then between 4 and 10 sub-steps within each of the main steps. It would seem logical to have the sub-steps vertically on the left side but I have a requirement that it has to run horizontally at the top underneath the main steps. None of the steps are selectable so you can't skip ahead or go back. The steps frame a separate function where multiple other smaller functions can occur, e.g. uploading multiple photos repeatedly to a gallery.
How would you solve this visually? Are there any working examples that I can refer to?
Thanks in advance from a UI designer thrown into a UX mess!