Tim,
From Frescobaldi menu: Tools | Special Characters -- my install has all three of the characters you mention (highlighted in the screen shot). This is the default view shown me when I select this Tool.
Depending on our OS you may find alternatives more useful. If you have a Windows computer, using ALT-Keypad# may prove useful. Once you know them, it's fairly quick, and a short guide will help. For example,
Good idea indeed.
On Linux I also use the handy map, it always bails me out :)
