I am a piano player. I use my computer keyboard and mouse in the Step Sequencer to create drum clips. One of my midi controller keyboards also has drum pads, but I find no trouble at all just clicking on the little boxes in the Step Sequencer to specify drum/cymbal hits. To undo an errant click on one of the boxes just right-click on the desired box and it erases the box.
By hitting the play button up at the top, it will loop through the beats for that clip, and you can keep adding/undoing drum/cymbal hits with your mouse until you are happy with that particular clip.
Cakewalk does NOT intend to have you use a drum map for any clips created with the Step Sequencer, and editing problems will occur if you do attempt it.
That means then that you will end up learning the note names and numbers that correspond to the various drums and cymbals and such for the given drum synth you are pointing to for the midi output for the track. That does not take long to master.
Also, you can preview a drum/cymbal sound by clicking on the left side of the Step Sequencer, in the place where the note names are. That way you can make sure you are triggering the right drum strikes when you are going to enter say kick drum. Clicking on the note name at the left will let you hear the drum sound for that row, without actually creating an entry into the matrix.
Bob Bone