I am working on a font called "Fantasy-8", which is a remake of the PICO-8 font - however, when I go to recreate the symbol "🅾️" (U+1F17E), I cannot because PixelForge only goes up to U+FFFF, and I'd ideally like my font to work by just copying-and-pasting in PICO-8 code. I would recommend you just tuck it away in an Edit>Goto Unicode Glyph option, without cluttering up the character set dropdown.

We can only hope that the developer either returns to this project or makes it open source. There is so much untapped potential in this tool due to minor limitations like this. I assume the limitation was put in place so that the user wouldn't be overwhelmed with a much larger list of ranges but it should definitely be an option even if it's less user friendly.