Select by lasso
MuseScore has a primitive box selection method for selecting parts of a measure. It's clunky and you can't add or subtract from the selection, but it's something at least...
Would love to be able to lasso a selection, like a graphic program. I can tell that MS sets graphics by segments so you can't exactly select the graphics on the page -- you'd be selecting whatever is in the segments in the selected area.
But a lasso select would be the same as single-slicking on a number of objects, but it would make it easier and quicker. Plus the user could select only the parts he needed -- stem, accidental, articulations etc.