New version, rewritten from scratch with Godot C#.
Glyph selection: In the Text Preview panel, you can now select glyphs by clicking on them inside the text, and the current glyph is highlighted.
Copy and paste: You can copy a glyph and paste it into another glyph. And you can auto-copy glyphs to their diacritics! That is, it will copy your already defined "a" into "à", "á", "â", "ã", "ä", "å", etc, so you can then add the diacritic and make other changes.
Fixed limits: Setting limits for width and/or height for the whole font. That way you literally can't place pixels out of that range, advance will be automatically set to that value (in case of fixed width), etc. Very useful for monospace fonts, and in general if you want to enforce a specific box.
Transform: New transform panel with tools to modify glyphs: Move, rotate, flip, scale. You can apply those modifiers to the current glyph, to all glyphs in current range, or to all glyphs in all ranges. Very useful particularly when you import a font and want to move up/down to meet a specific baseline, for instance.
Auto-save and recovery: Opened documents are periodically auto-saved to an internal folder. When a crash is detected, it will offer the option to recover the state of unsaved files, so you can save them manually after that.
Linux binaries available as well.