Two fonts opened in FontLab, Alpha and Beta. The only difference between the two fonts is, that one glyph is missing in Alpha. And that glyph is the left and the right partner of kerning pairs in Beta. Select the glyph from Beta, copy it and append (context menu) it to Alpha. And now check the kerning. Only the kerning of those pairs is appended, in which the copied and appended glyph is the left partner. The other pairs are ignored.
If you also want to have the kerning of the pairs, in which the copied glyph is the right partner, you have to select the appended glyph in Alpha and command "Paste special" (Strg+Alt+V) and in the dialog the check boxes for pasting the kerning must be activated.
This is a bug, isn’t it? Is it already documented? I have learned to be careful talking about bugs. This time I checked it three times. Can anyone verify, that I am right?