Sometimes you want to see an action in the context of its full project without losing your place. With a single action selected, Show Task In Project opens the corresponding project without disturbing your current view. Note that it works on one action at a time, not on multiple selections.
On the Mac, it opens in a new tab (or window, depending on your settings), focused on the project. On the iPad, it opens in a new window showing the action within its project.
Show Task In Project is especially handy when assigned to a keyboard shortcut, such as ⌥⌘J (J for “jump”).