How to add non-breaking space

Hi

How do I add a non-breaking space glyph is the unicode uniFEFF or uni00A0

Do I just do Glyph > Add Glyphs then add the unicode

Yes, or in the Font tab (Cmd-Opt-1), then go to the sidebar on the left, and right-click on Categories > Separator > Space.

Thank you

And is the non breaking space normal the same width as the space glyph
uni0020 or can it be set to 0

Yes, it is the same width. You can use a metrics key to make sure it is.