OK, it took me a fair while longer, but I got it sorted. For the benefit of others who might have the same problem and stumble on this thread, this is what worked for me, step by step:
- Go to Engrave -> Notehead sets
- Bottom-Left of left-hand panel: Create new (notehead set…) from selection (named Default Noteheads (1);
- Type new name for this set (top of top-right hand panel) e.g. “Noteheads between parentheses”, which is now echoed in the left-hand panel;
- Chose black note-head in the grid (in the top-rigth panel), click the Create new notehead from selection button (at the bottom of the right-bottom panel) [note: There are now TWO black noteheads in the grid. It is not obvious, but the Rightmost notehead is the NEW one, you want to edit. This is important…!];
- Give the new (rightmost black) notehead a new name (I don’t think this is important as such, but if the top left corner now shows a red triangle, you have selected the wrong notehead);
- Double-click on the new notehead in the grid to open the editor. Edit as needed (i.e. in my case chose parentheses and click “add glyph”, than move them to the right position) and click OK;
- Now, select the old black notehead (without parentheses) by selecting it and click “remove notehead from the set” using the button at the bottom of the top-right panel. This is also important!;
- Do the same for other noteheads (half/whole notes etc);
- Click OK to save;
To check: 8) Now go back to Write mode, select a (black) notehead, and go Edit->Notehead->NOteheads between parentheses, and it should show the new notehead (incidentally, and this is a bit of a mistery: if you -re-select Default notehead, it becomes smaller…)
(There may be other ways to skin this particular fish, but this worked for me).
Now, my understanding is that you can’t export this notehead set, so you have to go through this again for any new file you’re working on (or save a template).