If you want to model a layout, why not just use FileMaker. You don't need to create fields or scripts to do this. You can use the drawing tools and objects included in FileMaker.
Whatever you are comfortable with: Photoshop, OmniGraffle, Visio etc. Scribble on a piece of paper works quite good as well
There is a number of UI/UX prototyping tools, but I found it takes me longer prototyping with them than in FileMaker. The examples are Origami or Adobe XD.
You might even open each of the Starter Solutions and compare the "desktop" with the iPhone and iPad layouts (they all should have them). You can probably even see what theme works more to your liking, too, from the Starter Solutions. Just compare on your desktop and if you have some you want to explore more on iOS, then push them to it for testing. You can always delete.
Ok, I'll do that within FMP. I've started recording conversation with my patients then going back and listening to get what items I really need during each event, ie. consultation, follow-up, injectable sessions etc. I appreciate your answers. Dr. B