I know you can lock guidelines, but when I want to keep my left bearing at 0, it keeps moving when I start creating a new glyph or paste in an image. I always have to check the “Set left side bearing point at X=0” box to reset it to 0. Is there any way to lock that left side bearing at 0? Thanks! 
For now there is not much you can do about it, I hope to improve this in a later release.