Hey Erwin!
Something funky is up with the Preview window. It seems that if CALT is on, the more you add to the window the more the program starts to lag. I’m using the latest version of FontCreator 14.
Also, I don’t think there’s much you do about this but I was much happier with the shaping engine in FontCreator 13, but that’s just me.
Thanks for a great program!
Blessings,
Jonne