Hi!
I am so happy I found this wonderful software called High-Logic FontCreator.
Thank you so much to the creator!
I have a font that came with my cross stitch software.
The font is used to assign symbols to the threads used when converting a picture into a cross stitch design.
In the cross stitch software, I can see only 214 characters.
Opening that font in FontCreator, I was shocked to see there are 226 characters/glyps.
I even select the ones I can not see in my cross stitch software.

So, 226 - 214 = 12 characters I do not see at all.
I can see a .notdef, .null, nonmarkingreturn, space. Let’s ignore these 4.
What about the other 8 that FontCreator sees but my software doesn’t?

What can I do to those 8 characters so they can be usable?
Thank you!
The glyph overview side panel shows 8 glyphs that are “Undefined.”
Check their properties using the Glyph Properties toolbar (F4).
Yes, I see that, I accessed the “Undefined” section, I clicked on a glyph, pressed F4, then clicked the red button “Select Unicode character”, I chose one and after clicking Apply, the glyph disappeared. I did that to all 8, choosing different Unicode character.
I saved, exported as ttf, copied in the windows Fonts folder, open my cross stitch program and they do not show there…
What should I do?
From the User Manual
Note: only the first 224 characters of symbol fonts will be accessible: a space and up to 223 printing characters.
Convert the font to a Unicode font (from the Tools menu) to access more characters.
Thank you, I did not know that. Valuable information.
The convert to Unicode is not available. What am I doing wrong?

Then it is already a Unicode font.
Either you have not successfully replaced the old version with the new one, or your Cross Stitch software expects to find a symbol font.
Which Unicode code-points did you assign to the 8 undefined glyphs?