How to get max value in column chart

Hi!
In your "Max Orders Europe 3", remove Orders[Region] and Orders[ShipMode] from summarize so that the table is only grouped by quarter and not by those columns as well. This allows mulitple items to be selected.

Max Orders Europe 3 modified = 
VAR _table = 
CALCULATETABLE(
    ADDCOLUMNS(
        SUMMARIZE(Orders,
        Dates[Year], Dates[QuarterOfYear]
        ),
        "Totaal",[Sum Orders]
    ),
    ALLSELECTED(Orders)
)
VAR MaxVal = MAXX(_table,[Totaal])
RETURN MaxVal

You should also be able to remove ADDCOLUMNS() and make the measure a bit shorter, but maybe you prefer it that way:

Max Orders Europe 3 short = 
VAR _table = 
CALCULATETABLE(
    SUMMARIZE(
        Orders,
        Dates[Year], Dates[QuarterOfYear],
        "Totaal",[Sum Orders]
        ),
    ALLSELECTED(Orders)
)
VAR MaxVal = MAXX(_table,[Totaal])
RETURN MaxVal

Hope this helps!