I'm trying to create a tool font that will display latin letters and numbers but all other unicode code points will display an error character instead.
I can't leave the characters blank as for my use case this will result in the program falling back to a font that does have that character.
How do you use the same glyph for multiple characters?
Right click on the glyph > copy reference > paste into the new character
Now they are both linked and when you change the original it will change all the references.