Bob-
Original post says this is to split the drums into individual tracks to allow compressing/eqing each drum individually. Unless I'm missing something, you can't eq or compress anything in MIDI, only by audio processing.
David -
Yes, mute the drum in the drum synth.
You can also mute a step sequencer row across multiple step sequence clips. Select all the clips then click on the mute (M) button in the row you want to mute and it should then mute the same row in all the selected clips. At least, I've just checked in X3, it works there and as far as I can remember X1worked in the same way.
To mute notes in the piano roll view you select the notes then press T to bring up the tool box. The icon on the right (which is meant to be a scalpel) has two right-mouse click options, erase or mute. Select mute (the toolbox icon changes to an M) then left click on any of the selected notes and they will ghost out and be muted. Another left click unmutes them. A quick way to select a particular note/drum for the length of a song or a desired time period is to bring up the PRV and zoom out horizontally until all the area you need to mute is visible. Then zoom in vertically in the PRV until the notes are big enough to distinguish then select etc. as usual.