Slash Note Shape not what I specified

I am using slash noteheads with stems in a chords region. The quarter note slashes are as expected, but the half-note slashes are diamonds, not the parallelograms I expected, even after I set the half-note shape as a default in Engrave > Notehead Sets. I’ve been to Edit and Help, Write and Engrave modes multiple times, and have tried all of the Slash notehead alternatives. How do I convince Dorico of the shape I want?

Are you using a slash region created via Write > Create Slash Region, or are you inputting regular notes and then changing them via the Edit > Notehead submenu?

In a test I did just now, when I input regular notes into a standard notation staff, then changed them via Edit>Notehead>Slashes>Slash Noteheads, they converted as expected into (thin) quarter slash notes and parallelogram half-notes.

When I created a slash region and entered slashes (quarter note slashes were fatter than those in the regular staff, by the way), the half-notes had “white diamond” noteheads; the same Edit sequence as above did not change the diamonds to parallelogram Slash Noteheads as I expected, and which the user manual pictured.

I like the fat slashes in the slash region—easier for older players to read; but I prefer the parallelogram half-note heads in the standard notation region. What’s a body to do?

Off the top of my head, slash regions use the Oversized Slash notehead set. Sounds as though you may be altering the wrong notehead set.