I wanna say hold the Shift key then drag but last time I tried that in X2 it didn't work (I'm pretty sure it worked in X1). If your clip starts on a beat or measure you can just enable Snap and it'll snap into place. **If it doesn't you can use the Snap Offset by setting the offset to land on a beat or measure then it should snap into place. I'm not sure if offset markers copy along with with a copied clip.
**The manual seems to say offset doesn't work on MIDI clips. Still looking for the exact binding for drag and drop in place.
Okay, I'm not finding the info. Try Shift and drag or maybe Alt + Shift then drag. Sorry.