I have done a lot of line of business work over the years, and I would argue Excel is the perfect tool for prototyping processes.

Almost anybody can use it, it is simple and reasonably intuitive - and most importantly - extremely flexible, so you can change your processes and workflows without much cost.

Then once processes are figured out and reach a more stable state, you can turn that Excel process into something more smooth, custom software or a more advanced tool. And you have a pretty good starting point for a spec for the software.