Another one from my probably-so-simple-it's-silly file, but here's what I've got.
In one comp, I have an object whose transform properties are split so that X and Y are their own separate properties. In another, I have another object whose X and Y are together like normal.
What I'm looking to do is pretty simple, at least to explain: I want to parent the X property from the separate object to the X property in the one that's not, and same for the Y properties. (Yes I know the easiest answer would be to split the parent object, but I can't do that because this parent has a bunch of children, this one just happens to have a unique requirement.)
This is the expression that I've got on all the other children in the matched sets that have X and Y together:
"comp("1x2_300px").layer("Name 1 Name 2").transform.position"
With this expression it's easy because all the child has to do is inherit both X and Y properties and map them to its own. But when I apply this expression to the separated X and Y properties I get an error: "Must be of dimension 1, not 2."