We’re not associated with this site, but we use it all the time: PedalboardPlanner.com. It’s an interactive site that allows you to choose a Pedaltrain pedalboard, then load on and position images of pedals so you can make sure everything will fit, to try out layouts for pedals, to visualize ergonomics, and more! There are currently images for over 950 pedals from nearly 100 manufacturers, so even if the exact pedal you use isn’t on the list, you can likely find something that is similar in size and shape.
Once you’ve settled on a board layout, you can create an image of the result and drag it onto your computer’s desktop for reference.
Very clever and very useful!