You have not told us why you would want to run the scope like this. Why don't you trigger on the edge of the signal under test (or one of the signals)? That will give you one stable reference point on the horizontal axis of the screen.
If you prefer, shift the trigger time towards the left edge of the screen. You can also trigger on any (i.e. positive or negative) edge of the signal if you prefer that. If this does not work for your application, please indicate what's missing.
Edit: tpyos...