Show Only Top N In Column Level

You may not be able to achieve what you want in PBI, but here is something that is a workaround.

You need to unpivot your columns :

• Go to Transform Data

• Select your table 

• Select all WBS1 to WBS723 columns

• Right-click > Unpivot Columns

• Rename:

  • Attribute → WBS

  • Value remains as is

From :

To :

Then create 2 measures :

Total Value by WBS = 
CALCULATE(
    SUM('RawData'[Value]),
    ALLEXCEPT('RawData', 'RawData'[WBS])
)

WBS Rank = 
RANKX(
    ALL('RawData'[WBS]),
    [Total Value by WBS],
    ,
    DESC,
    Dense
)

Show Top WBS = 
IF([WBS Rank] <= 50, 1, 0)

The last measure you will use it as a filter on the visual.