Allow user to add musical and unicode symbols to the "Common symbols" section of Special Characters

Your idea

Calibre has an invaluable feature in its Insert character window: it allows the user to transfer characters from the general section to the Favorites list. This feature would make a welcome addition to the MuseScore repertoire.

See also, #23666.

Problem to be solved

IMV, the Special Characters facility is less useful than it should be because it does not have a transfer characters ability. The user is stuck with the default selection in the "Common" window or has to request addions in the github forum.

IME, unless the character is available in the "Common" section" it is difficult, if not impossible, to find, and I usually resort to adding from Linux's special characters window instead.

Checklist

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