Key signature editing: UI is unhelpful

Your idea

Creating and manipulating key signatures, even in their simplest form, is unnecessarily difficult. Each point individually is not a big deal, but as a whole they were annoying enough to make me write this list.

Don't get me wrong: It's great that the tool exists, and it seems to produce the correct results. I'm just noting that what seems like a simple drag-drop at first glance causes surprisingly much friction.

Problem to be solved

Take a look at me trying to add a reasonably okay-ish (possibly even "normal"?) key signature:

https://github.com/musescore/MuseScore/assets/2690845/1b1d7162-8799-4b84-a583-9151d1183811

Currently, when adding a key signature, there several things that can be improved:

Currently, "Create key signature" is hidden at the bottom of a hidden menu with several disabled items before it. Maybe that could be improved? After all, before any of the other options become relevant, "Create" has to be used at least once, so arguably it's used more often.
Currently, the "Key signatures" dialog (shouldn't it be called "Create key signature"?) doesn't offer a way to name the key signature. That can only be done in a different interface. I suggest merging these two dialogs.
Currently, the "Palette cell properties" (shouldn't it be called "Key signature properties"?) dialog offers no way to change the created key signature. I suggest merging it with the "Key signatures" dialog.
Currently, the "Key signatures" dialog contains a useless separator, that can be used to … I don't know, see the screen capture. I suggest removing it.
Currently, the "Key signatures" dialog window is too small by default, even though a slightly bigger window would easily fit all items on the screen.
Currently, the "Key signatures" staff widget, which I perceive to be the main input widget and entire point of the dialog, is tiny, and requires pixel-perfect mouse movements. I suggest making the staff much bigger, perhaps 200%?
Currently, when dragging accidentals inside the "Key signatures" dialog, the preview of the accidental while dragging is inverted in color, and occluded by the mouse. I suggest removing the color inversion to make it slightly more legible, and adding a "ghost" preview in the staff where the item would be dropped, so that it's a bit easier to estimate what's going to happen.
Currently, when drag-dropping accidentals inside the "Key signatures" dialog, the dropped/inserted accidental seems to have a lower y-position than while dragging. That seems like a bug to me.
Currently, the "Key signatures" staff widget only allows mouse-input. Even though there seems to be the concept of a "currently selected accidental", it cannot be manipulated using up/down arrows. Together with the previous point it's rather difficult to edit an accidental. I suggest supporting up/down keys like everywhere else in MS4.
Currently, the "Key signatures" staff widget does allow left-right reordering of accidentals, but is weird about it, and I don't understand what the mental model behind it is. In the screen recording, I place a C sharp, then an F sharp, and then notice that it's the wrong (non-canonical) order, and then can't reorder it. For some reason it is possible to place the same accidental on the same note way too far to the left. I don't get it: I suggest simplifying the model down to just a list of accidentals, such that the X coordinate is automatic.
Currently, the "Key signatures" dialog cannot be dismissed by pressing the escape key, like many other dialogs (Preferences, Parts, Format Style, Transpose, etc.) I suggest supporting pressing escape to close.
Currently, the "Key signatures" dialog has a grey "Add" button which does not close the dialog. I'm going to suggest that a "main action"-colored button and closing the dialog would surprise fewer users.
Currently, the "Key signatures" dialog has a text label that says "Create Key Signature". I suggest removing that label, because it's already in the dialog window title.

Prior art

Comparison Before: Bildschirmfoto_2023-06-22_16-02-41

Comparison "After", using way too much paint, just to demonstrate that making the staff larger would make it visually easier, and removing the unnecessary UI components doesn't even hurt: Bildschirmfoto_2023-06-22_15-50-29

Additional context

From the "About" dialog: OS: Debian GNU/Linux 12 (bookworm), Arch.: x86_64, MuseScore version (64-bit): 4.0.2-230651545, revision: github-musescore-musescore-dbe7c6d (This seems to be the identical binary to what's on the official download page)

The weird black borders around tooltips are an unrelated issue (15399).

musescore / MuseScore