I know that I’m not the only one who has been sticking with FontLab 5 despite the copy/paste issue that arose on Macs post-Sierra.
Just to let everyone know, the macOS 10.14.4 update kills it completely. Working with existing .vfbs still seems to work, but opening existing fonts is broken. OTFs will open, but their unicode assignments are missing and the UPM is messed up. TTFs won't open at all.
Just a heads up.