Query about generating a new MAX column on the table visual

Learner1810 try this:

Col6 = 
CALCULATE ( 
    MAX ( 'Table'[Col5] ),
    ALLEXCEPT ( 'Table', 'Table'[Col3] )
)

Hello Learner1810,
Thank you for posting your query in the Microsoft Fabric Community Forum.

I have reproduced your scenario in Power BI Desktop using the sample data you shared. By using the below DAX expression, I was able to generate the expected output where the Max Col5 correctly shows the maximum value of Col5 for each unique combination of Col2 + Col3.

Max Col5 =
CALCULATE(
    MAX(DataTable[Col5]),
    ALLEXCEPT(DataTable, DataTable[Col2], DataTable[Col3])
)

The ALLEXCEPT() function keeps the filters on Col2 and Col3 only, allowing the calculation to find the maximum value of Col5 across all dates (Col1) within those groups. For your reference, I have attached a .pbix file.

Thank you, parry2k for sharing your valuable insights.

Best regards,
Ganesh Singamshetty.