Relative expressions, beyond starting from "Root Container"

It seems a lot so, that I can’t refer components in expressions in
relation to themselves, but always must come from the window root.

Is this correct?

Example use for a relative referring would be when I’ve got
a group of similar objects whose logic repeats. I wouldn’t
have to hard-wire each separately.

When you create the components you are correct, the property path must be complete. After that they automagicaly modify themselves as you move/rename the components in the path so you don’t have to maintain them. It works very well. (unless you’re like me and keep pushing the boundries)