Optionaltransform_name?: stringPicks between definitions that share one type ("Fade In" and "Fade Out"
are both "fade") since their default params differ. dumpProject always
fills it; a hand-written document may leave it out and gets the first
definition of that type.
A clip effect as it travels in a document. The global definition is named by its stable
typestring (the same on every install) instead of its row id.