Locking the Editor View to a Camera
While the Matinee Editor is open, you can click on any of the tracks and it will automatically select the Actor (if the track is attached to an Actor) in the editor's viewport. With the Actor selected, you can then lock the viewports view to that Actor (a camera Actor for example).
Click the image for full view.
In box 1, a keyframe on the Movement track of Camera_1 has been selected. The camera assigned to the Camera_1 group in Matinee, Camera1, is shown as selected in the viewport in box 2 and selected in the World Outliner in box 3.
Inside the viewport, if you click the Viewport Options dropdown menu and uncheck the Allow Matinee Preview options...
Then click the Viewport Options dropdown menu again, you will see the option to Lock Viewport to Actor and the extended window will allow you to select the Actor to lock it to (Camera1 in this case).
After selecting to lock the camera, you will see a lock icon in the upper left corner of the viewport indicating that the view is now locked to an Actor.
While holding the Right Mouse Button down, you can now use the W, A, S, D keys to fly the camera into the position you would like for your shot at the selected keyframe, viewing it from the camera's perspective.
With the Right Mouse Button held down, you can also press the E key to move the camera up and the Q key to move the camera down.
You will need to re-enable Allow Matinee Preview after moving your camera in order to resume previewing the full Matinee sequence, but this method of locking the viewport to a camera is useful for moving your cameras into your desired positions.