"Melisma" / extender line for Roman numerals analysis

Your idea

Add a similar mechanism for the Roman Numeral Analysis(RNA) as for the lyrics where consecutive "_" will be transformed into a continuous melisma line.

For the RNA, this should be applied to the "-" and "=" signs.

Typing this:

Would be transformed into this:

Problem to be solved

In RNA, the following analysis, although apparently correct, doesn't make sense.

This leads to confusion, because a IV usually belongs to the the Sub-Dominant domain while in the measure 3, the IV belongs to the Tonic domain, as a Neighbour chord between to I's.

The same applies for the I64 in measure 5. It does not belong to the Tonic domain but to the Domibant domain as a Arpegiating Dominant chord (or Cadential64).

According to different sources, the correct notation for those cases is the following one (*):

Today, this is not possible to enter this notation.

This proposition will make this notation possible and easy to write.

(*) according (a.o.) to Clendinning/Marvin's "The Musician's Guide To Theory and Analysis" book:

Prior art

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Additional context

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Start by tracing the existing lyrics melisma mechanism and the Roman Numeral Analysis input path. Confirm how consecutive '-' and '=' signs are handled, then verify against the issue examples that each run becomes a continuous extender line without changing the analysis semantics.