I love this machine. Very beautiful project to suggest ideas how to evenetually improve it and how to code a state-machine it.
With your flow-chart and some additional answers to detail questions this will result in a beautiful and understandable state-machine.
There is another term that IMHO epxlains the programming-technique even better:
step-chain or step-sequence
The machine is doing well defined steps after each other. And even things like branching from a standard-sequence like
press the reverse-button to drive back the sheet is very easy to do
I really like this project and I will use it as a tutorial for explaining how step-chains (aka state-machines) are working. The tutorial will be taylored to your project. I'm very sure that you will understand the basic principle and that you will advance in your programming-knowledge.
Sending messages to the display is done as a inserted step into the step-chain that is executed just one time and then the code can go on with the next part.
For driving stepper-motors there is a library called MobaTools that is able to create the step-pulses "in the backround" this enables to do other things in the "foreground"
I don't have much time this evening. So please give the tutorial about state-machines a try and read it
As a newcomer to step-chains you will have questions. So please ask these questions I have the aim to improve this turorial again and again and again to make it understandable as easy as possible
best regards Stefan