Hi,
I test my font’s language support at http://www.underware.nl/latin_plus/validate/ and get %99 result. Only two letters are missing in my font.
IJacute (Unicode: E133) and ijacute (Unicode: E132)
I search them with glyph info and can’t find. Can I generate a unicode that is not exist in GlyphsMini?
PS: Maybe I’m a little obsessive. 
These Unicode points are in the PUA, and the name was invented probably by the Underware people. It does not have to be in the glyph info for you to add the glyph with that name and Unicode, and build the OT feature, of course. Any particular reason why you want this solution for the stressed Dutch IJ in the first place? It has a few downsides. One of them is that you can add the glyph, but you will not get it to work in Glyphs Mini, unless you get people to insert the PUA Unicode every time they want the glyph, which is not going to happen.
I suggest a different solution, please read this tutorial: https://glyphsapp.com/tutorials/localize-your-font-accented-dutch-ij
Thank you so much… I’m learning…