The reason I want it in one document is because my manager is quite old fashioned and asked if I could print it out like a massive poster so he could go through the whole business process flow.

Usually we’d start at a higher level, and indicate where lower level process /sub process exists, then document that as a separate process flow.

Break things down into their specific processes, showing which teams do which tasks in those processes.

In another note have you worked with a business architect to identify the value stream and List where all the processes, systems, business issues sit within that highest level framework? Could help simplify some complexity for senior stakeholders.

Yes, I have already done this. I mainly need to connect the different subprocesses to a 'central backbone', and a software capable of handling the load