X-Axis with two levels - Sorting should be different

One approach is to create a measure that generates a sort value that considers both the outer and inner dimensions in your visual. You then put the measure in the tooltips area of your visual, click on the ellipsis and sort by it. This example determines the total value at the outer dimension level and does the overall sort; the inner dimension is then sorted reverse alphabetically by name (but you could also use the measure value too).

NewSort =
VAR thisQty = [Total Qty]
VAR thisouter =
    SELECTEDVALUE ( Stores[City] )
VAR thisinner =
    SELECTEDVALUE ( Products[Subcategory] )
VAR outerrank =
    RANKX (
        ALLSELECTED ( Stores[City] ),
        CALCULATE ( [Total Qty], REMOVEFILTERS ( Products[Subcategory] ) )
    )
VAR innerrank =
    RANKX ( ALLSELECTED ( Stores[City] ), Stores[City], thisinner )
RETURN
    IF ( NOT ( ISBLANK ( thisQty ) ), 100 * outerrank + innerrank )

Pat