https://github.com/dolphinsmalltalk/Dolphin Dolphin had a 'view composer' but obviously it's a bit pining for the fjords.
Seems to still be kicking around: https://github.com/dolphinsmalltalk/Dolphin
Apparently last modified 8 days ago, with a history of infrequent but steady commits.
Caveat: Unfortunately only talks about Windows.
Dolphin Smalltalk is still being developed and is open source now: https://github.com/dolphinsmalltalk/Dolphin