Adjusting appearance of accents (and other articulations)

I find the default appearance of the accent marking " < " too large (vertically). I prefer a somewhat slimmer marking.
But I can’t figure out how to change the default appearance of the glyph.
(I ended up swapping to a different font from F*****)

When I go to the appearances options, I get the little window, see my desired glyph, click on it and have lines around it that should normally allow me to stretch horizontally or vertically. However it only seems to proportionately change the size. How could I get the glyph to be a bit thinner?

The x and y scales are currently linked, meaning you can only make the glyph bigger or smaller proportionally. If you find a glyph in another font that you prefer, you can both bring in that glyph and delete the existing one from the right panel of the editor.