Your editing and explanations are meticulous and thorough. But you are missing a couple of features that actually make these engrave mode adjustments unnecessary:
- Once a syllable has a duration, it can be altered with Shift+Alt+arrows by the grid so the extender is exactly the correct duration to accommodate all the parts
- If you prefer melismatic syllables left-aligned, we can override the alignment case by case in Properties
Both of these can be done to multiple syllables at once.
Bonus technique: Instead of adding and deleting Soprano notes to match another part’s rhythm, just split and re-tie the existing note. Place the caret at the last note of another part’s melisma and U the S note, fix up the lyrics, then select the first S note and T to make it one note again.