Another couple of small suggestions:
-Move the "Clear Glyph" button from the Glyph tab to the "Edit" menu next to the copy and paste Glyph and bind it to the "Delete" key.
-Bind the functions from the Transform tab to keyboard shortcuts - for example move could be Ctrl+Arrow keys, rotate could be R / Ctrl+R etc.
-Include a link to a site like https://unicodeplus.com/U+00E7 when clicking the text with the Unicode and glyph name in the Glyph tab. Maybe also show the unicode and glyph name in the footer? (next to the number of glyphs in the font)
-Add a button "Clear unmodified Glyphs" - useful when you copy glyphs to diacritics, but don't want to edit them all, and have to go through and clear them one-by-one afterwards.
-Copy Glyphs to Diacritics doesn't work for the Latin-3 and Cyrillic ranges.
-Right-click a glyph to preview it as a reference to the left of your current glyph (similar to the ghost preview to the right)