“Normalize: Two Pass” does not allow keyframing. Any keyframe-line you created was not associated with the Normalize filter. So we are unsure of how a clip is being divided into six sections when you say “keyframe-line”. Can you send us a screenshot?
More generically, what is the overall goal? To have all six sections be -23 LUFS each? If so, then “Normalize: One Pass” may be a better filter to use. See its description here:
“Normalize: Two Pass” may not be the right (or easiest) choice because it scans the entire clip (not just the keyframe-line section) and computes the average loudness. Let’s say the analysis found -26 LUFS integrated as an example. Two Pass then adds a fixed gain offset to make the entire clip hit the target, not just a keyframe-line section. For this example, it would raise the gain of the entire clip by 3 LUFS to hit the target of -23 LUFS. After that, adding additional “Normalize: Two Pass” filters would do nothing because the additional filters would see audio that is already on-target from the first filter, and therefore apply a zero LUFS offset which is effectively doing nothing.
Once we know where the keyframe-line is coming from, we can address the next step of modifying audio levels per section if “Normalize: One Pass” is not sufficient.