Accessibility: need accessible equivalent for click / Shift+click for selection

Describe the bug
MuseScore supports the standard click / Shift+click method of selecting a range, and this also works for selecting elements of a given type within a range (all lyrics in a given range for example), but there is no accessible way to do this.

It's a complicated issue as MuseScore doesn't distinguish the act of "selecting" an element from the act of "navigating". So if you select the first element, there is no way to navigate to the last without losing the initial selection.

I can imagine solutions to this - like a new "mark element" command to mark an element as being selected, and then after navigating to a new element, a "select to mark" command you could use that would be the equivalent of having clicked the first and Shift+clicked the last. But, probably there exist other designs for this sort of selection out there that could be leveraged. Certainly lists that allow multiselect are one example, but I don't know that there is a standard for how to do this.

Of course, Shift+cursor is an alternative to extend a select an element at a time, but it's not as nice for selecting very large ranges where you might have otherwise used something like Ctrl+F to move from one end of the selection to another. it's also not possible to build list selections this way (eg, click / Shift click of lyrics).

No files, tests, or entry points are named. Start by researching how MuseScore separates selection from navigation and how accessible multiselect is handled in comparable list interfaces. Done means providing an agreed accessible equivalent for click/Shift+click range and list selection.