This is a judgement call, but we recommend keeping processes relatively small and their contents functionally related. For example, if you do bioprocessing you might make material preparation as one process, fermentation another process, and HPLC analysis a third process, all of which can be linked together to form a complete overall master process.
Another criteria that might suggest process boundaries is the team that executes it. I.e., it’s often helpful for each team to define, execute and improve their own process independently. Again, this is an argument for dividing bioprocessing into material prep, fermentation and HPLC analysis — because three different functional teams execute and improve upon those processes. Don’t worry, if you break it up this way, you can still pass samples, materials and equipment between the processes.
If you do want to make separate processes and then link them together into a master process, be sure to export the input and output resources that you want to use to link the processes together. That will make those resources visible to other processes.