I was asked to create a program that would assist accountant to aggregate data from various sources and generate some complicated analytical reports. Since this is an internal utility, I see it as desktop program for Windows – I choose WPF since UI may get sophisticated. But before I start actual coding, I’d like to show concept to accountant (so I won’t have to re-do things, also it is good for communication). How do I make a prototype of UI for a review?

Here are options I have considered before asking this question:

• Gimp. I did prototype of UI in GIMP but it is time-consuming. Maybe there are some other options?
• Draw it in DXF in QCad . It will be pretty schematic but faster than in Gimp
• Create it using Figma. I have seen mentioning of this service for exactly same tasks, but it seems used for extra-fancy UI, and I did not find support of regular Windows 10 User Interface. Apparently people use it mostly for Web design or for Mobile UI but not for Desktop programs

So, how do I effectively prototype User Interface of desktop program ?