Unless I’m missing something (very possible) the kerning does not work in Glyphs 3 with Catalina. When I use 10.13, it shows and works as expected.
What exactly do you mean. Can’t you edit the kerning or is the kerning not working in the exported font? In what app?
have you read this https://www.glyphsapp.com/tutorials/eliminating-font-cache-problems?
I’m not sure how else to say it. When I place the cursor between two letters and apply kerning values - either with a keystroke or manually - the space between the two letters does not change. This is with G3 on Catalina. It is not for an exported font.
Can you check the small icon in the lower right (the ‘To’): Click on it until it looks like this.
my apologies, this must have been off.