If you’re using OmniFocus Pro and you want to concentrate for a while on a particular project, folder, or combination of items, the Focus feature can get everything else out of your way.
Select a project or folder (or any combination of projects and folders) in the sidebar or main outline.
Click the Focus toolbar button, choose View ▸ Focus on (Selected Items) (Shift-Command-F).
Everything outside your selection disappears from the sidebar, the title at the top of the window changes to Focusing on (Selected Items), and the focus bar appears beneath the toolbar to indicate that you’re in a special view of your database.
As you move between perspectives, OmniFocus ignores everything outside of your focus, as if the items you’re focusing on are the only items in your library.
When you’re done focusing, choose View ▸ Unfocus (Shift-Command-F), or click the Unfocus button in the focus bar. Your library comes back as if nothing ever happened!
When you find yourself using a certain set of contexts, focus, and view options pretty often, you might want to save them as a custom perspective.
Focusing inside a custom perspective that includes a focus as part of its parameters will display the intersection of the two focus areas.