Sorry for resurrecting this thread, but I am having the same problem in trying to implement a cancel button in Vanilla for a long running process (Cancel button for scripts with long runtime)
Is there a way to update or poll a Vanilla control from Glyphs? The GUI freezes if I run a long process, even if the process is in its own thread. And attempting to open a Vanilla window in a separate thread causes Glyphs to crash.