How to list files where certain field contains file.name AS a field inside a query/WHERE as a Field

[Bluemoondragon07]

Sorry if the wording of the title is confusing, but...I'm really confused on how to do this.

So, I have these Location notes a project I've been writing. Some Locations have the field mother-location. If mother-location is null, then the file is a mother location. If a Location has a value in mother-location, like mother-location:: [[United States]], then that Location is a sub-location of the United States.

I've been trying to have a table list mother locations only and show their sub-locations as a field. This field is meant to show files where contains(mother-location, file.name).

I've been trying to use the filter() function, but I have no idea how to use it. I don't understand why => is used and why a value enclosed in parentheses is needed before it. I'm not even sure if it is the function I should be using. This is my query so far:

TABLE (list(filter(file.outlinks, (mother-location) => contains(mother-location, file.name)))) as "Sub-Locations"
WHERE mother-location = null and contains(file.folder, this.file.folder) and file.name != this.file.name

You can probably tell what I'm trying to do, but...I'm clueless as to how to get this working. It's kind of like putting a WHERE statement inside a field. I want to filter outlinks to only show those where mother-location contains file.name. I just can't figure out how to do it.

If you know of a way to achieve this, please share the solution with me. Thanks for reading this, and have a great day.