When you're at work, you don't want to see your personal tasks, and the other way around.
What can help
Categories
In the Master List, sort your tasks and projects into Work and Personal categories. The Global Filter uses these categories to know what to hide. Categories are always available, there's nothing to turn on.
Global Filter
Mark which categories are for work and which are for home. The Global Filter then hides everything from the other side throughout the whole app, so work and personal tasks never mix.
Ideas to try
Work and Personal. Set up two main categories, Work and Personal, and put everything under one of them.
Switch with one click. Create a Work filter and a Home filter in Global Filter. Add Global Filter to your Main Menu or Sidebar from its Access tab, then switch between them there. Everything from the other side disappears throughout Marvin until you switch back.
How to turn on a feature
Open the main menu and click Features, or press S.
Search for the feature by name and turn it on.
Choose where you want to reach it in the Access dialog that opens.
You don't have to try everything at once. Pick the one that sounds most like you, use it for a few days, and see how it feels.