Is it possible to move the lines on a staff with a plugin?

Looking at this previous forum post by robertmengual: Create new custom music notation, this might be just barely possible, but I'm not sure.

Based on the replies by jeetee and illionas, my best hope so far seems to be "not displaying the staff lines" and "adding 'TextLine's manually and moving them to the correct vertical location", and one of the limitations is that it is "not possible ... to make the middle staff line disappear".

Luckily in the Guitar Open Lines notation I'm trying to make, the middle staff line is still there. The middle line in a standard guitar treble-clef-down-an-octave staff is a B, luckily one of the open strings on a Guitar in standard tuning is that B.

However I still have questions:

(1) How do I make all the lines except for the middle line and the line below that disappear? On a treble clef I would like to keep both the G and B lines as they are if possible.

(2) Do the 'TextLine's need to be added manually... like by hand to visually match the correct vertical location, or can a plugin tell it where to go based on steps, such as steps above/below that middle staff line?

(3) Would custom ledger-line positions also need to be 'TextLine's, and would those need to be added manually as well?

(4) For possible automation of this in a plugin, would it need to be aware of system breaks, and need to re-traverse the score every time the system breaks change? How should that work, or is it possible to avoid that?

The code I'm trying to write crashes MuseScore if I try to add the TEXTLINE elements to the score with a cursor. Specifically if I uncomment the // cursor.add(sl) in the code below, it crashes. I'm obviously doing something wrong... what do I need to do to add the TextLines properly here?

import QtQuick 2.0
import MuseScore 3.0

MuseScore {
  menuPath: "Plugins.guitarOpenLines"
  description: "Guitar staff notation with Open string on Lines"
  version: "1.0"

  function scoreGuitarOpenLines(sc) {
    console.log("hello Score")
    for (var i_pa = 0; i_pa < sc.parts.length; i_pa++) {
      var pa = sc.parts[i_pa]
      if (pa.shortName == "Guit." && pa.hasPitchedStaff) {
        partGuitarOpenLines(sc, pa)
      }
    }
  }

  function partGuitarOpenLines(sc, pa) {
    console.log("hello Part")
    var startStaff = pa.startTrack / 4
    var endStaff = pa.endTrack / 4
    sc.startCmd()
    sc.selection.clear()
    sc.selection.selectRange(0, sc.lastSegment.tick + 1, startStaff, endStaff + 1);
    sc.endCmd()
    var cursor = curScore.newCursor();
    cursor.voice = 0
    cursor.rewind(Cursor.SELECTION_START)
    cursor.staffIdx = startStaff
    createStaffLines(sc, cursor)
  }

  function createStaffLines(sc, cursor) {
    // relevant style keys: staffLineWidth, ledgerLineWidth, ledgerLineLength
    console.log("hello createStaffLines")
    var offsetYs = [0.5, 2, 3, 0.5, 2, 3.5]
    var placements = [0, 0, 0, 1, 1, 1]
    for (var i = 0; i < 6; i++) {
      var sl = newElement(Element.TEXTLINE)
      sl.offsetX = -8
      sl.offsetY = offsetYs[i]
      sl.lineWidth = sc.style.value("staffLineWidth")
      sl.placement = placements[i]
      // cursor.add(sl)
    }
  }

  onRun: {
    console.log("hello world")
    scoreGuitarOpenLines(curScore)
    Qt.quit()
  }
}

The goal for now is to add 6 TextLine elements, 3 of them at positions 0.5sp, 2sp, and 3sp relative to the top of the staff, and 3 more at positions 0.5sp, 2sp, and 3.5sp relative to the bottom of the staff.

I'm also hoping that if I add them with a plugin, the TextLine Segments created after system breaks will also keep those positions just as they were before the system break.

Since MuseScore crashes when I run this with the // cursor.add(sl) line uncommented, I don't know how to recover any useful error message.

Using the Score Comparison Tool between the score before and after adding the TextLines manually, I was able to get the Diff showing the kinds of elements I would need insert:

(see file attachment below, using a markdown codeblock didn't work because the markdown parser still interpreted the XML tags within the codeblock as html I think, that's probably bad)

So that's where I may turn to next with a "plug out" kind of thing if I can't insert these TextLines with a plugin.