How to overdub/layer MIDI takes?

I'm not sure what you mean by 'the second take is inserted before the first take'. If you enable Sound on Sound record mode, takes will be layered (i.e. all takes sound together on playback) with each take recorded into a separate lane to facilitate editing. Some users would like to have the ability to automatically 'merge' multiple takes into a single clip, but SONAR doesn't do that. You can select all clips and Bounce to Clip(s) or use Flatten Takes to do that after the fact if you really want to. Personnally, I prefer to keep separate parts of a drum pattern separate for the most part, though I often record kick and snare in one take, hi hat articulations in another take, tom fills in another take, etc.