[garylz] “Is there a way to make a new timeline of a part of an existing timeline?”
Create a new sequence (File>New>Sequence). Then from the Project window, drag the sequence icon representing the sequence you want to import into the new blank sequence…trim as needed.
[garylz] “so I can edit them together”
You can edit audio at the Track level using the Audio Mixer. But beware- the keyframes become part of the track and not the clips. Do this only after you have finished editing video completely, as moving any clips after editing with the audio mixer will cause much consternation!