You can add flams, that is, short secondary drum hits just before or after the actual main drum beat. You can add up to three flams for each pattern step.
In the lower left section of the Beat Designer panel, you can set the positions and levels for the flams you created.
The first Flam Positions slider specifies the flam position for all steps containing one single flam, the second slider the flam positions for all steps containing two flams, and the third slider the flam position for all steps containing three flams.