Use modifier key to constrain movement when dragging notes horizontally

Your idea

Allow using the Shift key to constrain moving to horizontal

Problem to be solved

Occasionally, I need to shift a chord at the beginning of a measure to gain a little more space. I click on a note, and drag it to the right. Often, if I'm just a little sloppy with my drag, it moves that note up or down. In many drawing programs, holding the shift key while dragging constrains that drag to horizontal or vertical (and often to 45 degrees or a preselected diagonal.) While I certainly don't need all of the options, being able to worry about one thing less would be helpful.

Prior art

No response

Additional context

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Checklist

• This request follows the guidelines for reporting issues
• I have verified that this feature request has not been logged before, by searching the issue tracker for similar requests

Start by locating the C++ desktop UI entry point that handles dragging notes and modifier-key input. Implement horizontal movement when Shift is held, then verify that ordinary dragging still permits the existing movement behavior and that the requested chord-spacing workflow works.