Apply query changes getting stuck (small dataset)

Yes, SQL Server.
I'm trying to add it in Power Query, I don't know of a way to add it in DAX.

I didn't specify an SQL query in the advanced options when I imported. I can view the native query and see the full query fold and the lines of data where it put in the conditional column with a CASE statement:

select [_].[Yr] as [Yr],
    [_].[MonthNo] as [MonthNo],
    [_].[amt] as [amt],
    [_].[gltr_domain] as [domain],
    [_].[MonthEnd] as [Date],
    [_].[Currency] as [Currency]
from 
(
    select [_].[Yr] as [Yr],
        [_].[MonthNo] as [MonthNo],
        [_].[amt] as [amt],
        [_].[gltr_domain] as [gltr_domain],
        [_].[MonthEnd] as [MonthEnd],
        case
            when [_].[gltr_domain] = 'usa'
            then 'USD'
            else 'Other'
        end as [Currency]
    from 
    (
        select [_].[Yr],
            [_].[MonthNo],
            [_].[amt],
            [_].[gltr_domain],
            [_].[MonthEnd]
        from [DATABASE].[TABLE] as [_]
    ) as [_]
) as [_]
order by [MonthEnd],
        [gltr_domain]

I did not write the M code myself. I only used the dialog box that pops up below. So the code in the native query is just what PBI wrote for me.