Imagine Math Facts is currently geared to determine which facts the player already knows and proceed accordingly. It will then optimize fact order and instruction to maximize retention. Customized skipping or re-ordering is not available within an individual operation.
You can, however, set operations ordering so that students must play through the 4 operations—addition, subtraction, multiplication, and division—in the order you specify. To learn more, refer to the table in step 8 of Creating a class in the Imagine Math suite.