Hello, Roger
The advice to pay attention to the aha moment of recollecting the object of meditation occurs at all stages that one is losing the object not just during the 4-step transition to the breath at the nose. When you do have an “aha” moment then make a mental note of that to reinforce this in the subconscious, then make an intention to return to where your meditation was before, which can be anywhere from Stage 1 – Stage 4 really. You are developing the skill to have your mind do this automatically in the later stages at an even more subtle level.
I recommend that you do the 4-step transition for a set period of time and then move on to the breath at the nose as the object because you seem to have this mastered quite well.
Regards
Michael