How to control the slicers?

Hi bourne2000 

As you've noted, the built-in "Percent of grand total" calculation calculates the total based on the overall filter context of the visual (using ALLSELECTED in the DAX query generated).

To calculate % of total for all Categories including those not displayed, you will need to create explicit measures and use REMOVEFILTERS or ALL.

I recommend creating:

Amount Sum = 
SUM ( YourTable[Amount] )

Amount % of total = 
DIVIDE (
    [Amount Sum],
    CALCULATE (
        [Amount Sum],
        REMOVEFILTERS ( YourTable[Category] )
    )
)

(applying a percentage format to the second measure).

Does this work for you?

Regards,

Owen