In the timeline, you can copy a video, audio clip or image and paste it into anywhere in a track.
On a track, select a file you want to copy, click the right mouse button open a drop-down menu. Select "copy". The keyboard shortcut is Ctrl+C.
To paste a clip, drag the cursor to a position in the timeline, click the right mouse button on the selected track, and select "paste". The copied clip will be pasted into the position of the cursor. The keyboard shortcut for paste is Ctrl+V.