[Solved] X3 audiosnap

Set the Edit Filter on the kick track to Transients and make sure that clip is selected.

If a clip has been added to the pool, there will be a check next to Add to Pool in the context menu and clicking Add to pool again will remove that clip's transients. But I don't think the pool content has anything to to with Copy As MIDI. So long as you have only one the one track/clip selected when you copy, you should only get the kick transients. Have you set the Threshold properly to disable snare bleed transients on the kick track?
 
 

I'm thinking you must have executed the Apply Transient Pool Markers function on the kick track with the snare transients in the Pool at some point. If that's the case, you can right-click and select all User markers, delete them, and then lower the Threshold slider on the Kick track to re-enable the kick markers.
 
EDIT: Right-click > Associated Audio Files > Recompute Pictures may be the faster way to get rid of the User markers. Otherwise you have to bind some key combo to Delete Marker to make it easy to delete multiple markers quickly.