DAX function to count matched text values among rows

Hi,

I suggest having an additional table like below for creating a slicer.

Please check the below picture and the attached pbix file.

It is for creating measures.

Category measure: = 
IF (
    HASONEVALUE ( 'Item'[ItemName] ),
    MAXX (
        FILTER ( 'Item', NOT ( 'Item'[ItemName] IN DISTINCT ( Category[ItemName] ) ) ),
        'Item'[Category]
    )
)

Number of overlapped category: = 
VAR _selectedcategory =
    DISTINCT ( Category[Category] )
VAR _currentrowitemnamecategory =
    SUMMARIZE (
        FILTER ( ALL ( Category ), Category[ItemName] = MAX ( 'Item'[ItemName] ) ),
        Category[Category]
    )
RETURN
    IF (
        ISFILTERED ( Category[ItemName] ) && NOT ISBLANK ( [Category measure:] ),
        COUNTROWS ( INTERSECT ( _selectedcategory, _currentrowitemnamecategory ) )
    )