I can do many different projects if the tasks across projects are similar.
I can do many different tasks if they are in the same project or across similar projects.
But I cannot do many different tasks across different projects if the projects or the tasks are far too different from each other…
Unless I have a to-do list which organizes by time and / or location.
“[ While in [x] location / While during [y] time ] DO Geographical / Time Task a, b, c, d, e, a, f”
When life happens, having starting and stopping points within each project and each sub-task, you can stop what you’re doing and get back to it later.
If you have a lot of non-project tasks (such as life) that can come at any moment at any time, having a logical subdivision of the tasks into subtasks or subtasks of subtasks, allows you to continue where you left off.
With training, you can learn to manage many projects this way, so long as there is something functioning as an index or memory cue to allow you remember the ‘next step’ of each, no matter how many projects you are simultaneously task switching.