I have a lookup from a Query which shows up in the data editor (but it is grey within the cel) but does not show up in the Layout Editor when I try to use it.
I have the same exact lookup for a Relation which shows up in the data editor (but is aqua within the cel) and it DOES show up in the Layout Editor.
A lookup through a Query column is the same as a lookup through a multiple relation in that it will always return an array. If you want the same as you would get with a lookup through a single relation, then you need to use a single value column instead of a lookup.