“Imagination is more important than knowledge.” That’s what Einstein, renowned for laying the foundation for many of his theories in pure imagination, allegedly said.
There is a limit to the amount of data we can store (simultaneously) in our imagination. I call it; the mind’s RAM. (RAM stands for read access memory and in terms of devices, more typically means a faster device with more computing power.) Our mind’s RAM size is variable. When you’re dealing with a lot, haven’t slept properly, it’s smaller than when you’re fully rested and focused. More is better. For us regular folk, it’s typically a lot smaller than Einstein’s mind RAM.
To conceive something complex, with contingencies and multiple outcomes, out of the blue, is difficult. Use your imagination until the point where your mind’s RAM overflows. Defer to pen and paper after that. Only then to move on to a device.