In the past days there were some questions concerning Do not match.
Maybe it is a good idea to have a separate menu entry for "do not match" (or a group of corresponding settings) with the symbol itself and the indication of its unicode value, e.g.
etc.pp. A deluxe version could even allow to enter a sign and the Unicode is automatically displayed in a secound field, or even vice-versa.
The actual display is rather confusing.
If you think this extra menu is too special, I agree (although the left column on the Preferences pane offers enough space). But why not make a second level of Preferences that needs to be extended by clicking on a button/text? This would make the day-to-day preferences less complicated and allow rookies to explore the settings from the easy to the complicated ones. In the end this is very similar to the solution with the hidden menus.
Just some thoughts ...
Just the opposite. Unicode numbers are much less intuitive than actual characters. Nonetheless, in one of the latest 2018 Forerunner versions there is an option to add characters in the form of Unicode numbers to the "Do not match" list if you prefer so.
> why not make a second level of Preferences
That would go in the directions of "Airbus" design. I prefer to stick to the "Cessna" approach with shy ventures into "Tesla" territories. :)