Clusters notation

Your idea

I propose to implement cluster notation for keyboard instruments. There are several spelling options, I will try to describe the most suitable ones (in my opinion).
Many people know that the history of clusters originates from Henry Cowell. It is his way that I propose to use. For a better understanding of his notation, I suggest you familiarize yourself with his works.
I will note only a few points concerning some of the features of the designation of certain variants of clusters.

1. For clusters with a narrow range, use the vertical bar on the left (but after the accidentals).
   
   
2. To indicate the approximate pitch of the cluster, use a rectangle that can be adjusted both in range and vertically.
   
   

Problem to be solved

This notation will be a good alternative for those cases when it is necessary to designate a cluster with a large number of notes. Agree that it is too hard to read this kind of chord:

In this way, musical notation can be simplified, and although I take into account what @LupusCaeruleus outlined in his issue #17503, I still think that notation with note clusters is more convenient.

Prior art

No response

Additional context

Note that the appropriate notation for clusters requires the appropriate glissando line notation. Recently, I had the need to stretch the glissando from the cluster to the highest note by 4 bars (in the string section). I was barely able to get the look I needed, but the appropriate sound can only be dreamed of. The fact is that for a glissando from a cluster (or to a cluster), the glissando line should be in the form of a strip, the width of which depends on the width of the cluster range. I met this notation in Wojciech Kilar's Riff 62, which shows how a cluster created by 36 violins using three strings (G, D and A) slowly rises up, ending with the highest note of each of the three strings of 36 violins.

I would like this to be taken into account when implementing such a notation. In my case, it was a little simpler (because the cluster was not so wide in range), but the essence was the same: it was necessary to designate a glissando from a cluster consisting of 3-4 notes and divided by each note into a string to the highest note (at the same time, the instruction "maintain the cluster" meant that each of the the strings had to reach the highest note, but at the same time synchronously (without advance or delay) with other strings). That's what I managed to do in the end. I would like more.

The issue proposes cluster notation for keyboard instruments, including adjustable cluster shapes and related glissando lines, but names no source files, tests, or entry points. Start by locating the existing notation and glissando implementation; done would require an agreed design covering the proposed notation and playback behavior.