Custom name for PUA glyphs in Glyphs Mini

I use Glyphs Mini and I try to create a set of my custom glyphs (basically icons). Most of them are in the Other category. I want to be able to insert them in other software using Character Viewer on macOS.

I assume I should assign them to Private Use Area (PUA). I followed steps from official Glyphs Mini handbook:

You first create them with a name according to the uniXXXX (for values between U+0000 and U+FFFF) or uXXXXX scheme (for values beyond U+10000) to set their Unicode value, and then rename them to your liking.

Once I name the glyph to uni0003, it has unicode assigned. However, when I try to rename it “to my liking” (let’s say myIcon), the Unicode is lost.

What am I doing wrong?

0003 is not a useable Unicode.

For this to work properly you need to use a Unicode from the Private Use Area. The first range starts at E000 (those are hexadecimal numbers).

Thank you!
U+0000 misled me. Now it works!