The feature you’re using here (n your screenshot) is not “sort by”, it’s “change the field we should look at to sort by”. Consult the reference for details on how that works, but I don’t think that is what you are trying to do. (I’m mobile at the moment.)
The Sort field in the Search configuration dialog will only let you select a field that exists on the Thing you are searching.
You can also add :sorted by after the fact. But again, you can’t take some arbitrary list and and use that as a sort criteria.
But it sounds like you’re trying to do a different “mapped sort”?
A mapped sort is like this:
Let’s say we have a list of Users which I will represent below by first name. The list is:
Amy, Pedro, Petra, Becky, Thomas, Keith
And now I have another list that corresponds to some other quality. Like, let’s say that (I think this is what you are trying to do) Amy is going to 5 concerts in the future, Pedro is going to 6, Petra is going to 1, etc.
And that list is:
5, 6, 1, 2, 30, 3
Put in tabular form:
User # of concerts
Amy 5
Pedro 6
Petra 1
Becky 2
Thomas 30 (Thomas really likes concerts!)
Keith 3
And now we want to sort the number of concerts (Descending) and have each User follow along. So that we would get:
Thomas
Pedro
Amy
Keith
Becky
Petra
Well, Bubble cannot do that… Unless # of concerts is a field that’s already on the User object.
Then you’d just sort by User’s “# of concerts” field.
Of course, this is a little bit annoying.
The SORT List feature in my List Shifter plugin lets you do this, however. If you load the list of Users into List Shifter, you can then run List Shifter’s SORT List action on it and supply the # of concerts list as the list to sort on.
Is this something like what you are trying to do?