簡単な方法で動画を分割させたい

Choose the Replicate Fx in your Effect Panel.

Not sure I understand.  Do you want to shrink a clip and repeat it in the frame?  You might find a prefab effect in something like fxfactory . https://fxfactory.com/

But it shouldn't be too difficult to build this yourself.  Just edit the clip in the timeline, go to the effects controls and scale and position as desired for the top left.  Duplicate this clip in the timeline directly above the clip and adjust the vertical position for the left center.  Than repeat and adjust the vertical position for the left bottom.  Then duplicate the 3 clips, and place above the existing three and adjust the horizontal position of the three new clips so they sit in the center of the frame.  And then repeat so the new duplicates sit on the right side of the frame.  Make sense?