If you own, or are a member of, multiple workspaces, it can be tricky to keep track of not only your own tasks, but tasks you're subscribed to. The best way to stay up to date with everything going on across your workspaces is to use the Overview workspace.
The Overview is a more focused, personalized space with a Favorites section dedicated to projects and tasks that you're subscribed to. To clarify which workspace the task belongs to you'll see an additional workspace field in the task form and in the project view the project name will be prepended by the workspace it's currently in.
To open the Overview workspace, click workspace name at the top of the sidebar. This will open the workspace switcher; you can see all the workspaces you belong to here. To jump into the Overview workspace just click "Overview" at the top of the switcher.
Once in Overview, you can work in the several different projects offered in Favorites, including the Dashboard, Calendar, My Tasks, Subscribed, and Delegated. Projects that you or other users have created do not appear in the Overview workspace's sidebar, though tasks in projects you are subscribed to will appear in one of the various Favorites projects.
Like your other workspaces, you can create tasks in Overview, you just need to indicate in the task form which workspace the task should be added to. Editing, commenting and completing tasks are all the same as in other workspaces.