you can appkly a discount to multiple items at a time by using a cart column to group items into a discount catagory.
create a new cart column named discountCategory for items that should get one discount, set this column value to 1, for items that should get another discount, set the column value to 2 and so on.
you can then create dicounts for each discount category using the trigger :
"Number of Items with a specific column value"
If the number of items where "discountCategory" has a value of "1" is ">=" a value of "10"
and using the calculation:
"Based on items with a specific value"
Total of "TotalPrice" where "discountCategory" has a value of "1" "times" "0.25"