I want to insert a new, short video at the beginning. How do I move everything to the right? Don't I first have to lock everything on all the tracks in place so everything moves to the right as a unit? Otherwise, wouldn't I just be sliding the earliest track under the others?
If I'm following your question correctly? You want to slide media contained in multiple tracks to make room for a video at the beggining of a project.
The easiest way is to use the Playhead. Place it at the beginning of the timeline and "Hold Down Shift" This allows you to Drag all the media on the timeline to the right. Drag it far enough to make room for the new clip.
Drag in the new clip.
Place the playhead next to the media you moved. Hold down Shift again. Drag it back. You can over shoot the new video with the playhead.You don't have to be careful about it.The other media stops moving when the playhead bypasses the leading edge of the inserted clip.