https://docs.inductiveautomation.com/display/DOC81/property
You can in Perspective, actually 
I would have expected {parent.parent.parent.etc} to work, honestly.
EDIT: It looks like an intentional restriction that I don't see a way around. I'm not sure what technical limitations are implied; someone else may have more luck playing around with things:
https://files.inductiveautomation.com/sdk/javadoc/ignition81/8.1.15/com/inductiveautomation/perspective/common/api/PropertyRef.html