manual/include/moving-markers.html

<h2>Single marker</h2>
<p>
  <kbd class="mouse">Left</kbd>-click and drag to move a single marker to a
  new location on the timeline.
</p>

<h2>Multiple markers</h2>
<p>
  It is possible to move multiple markers by the same distance. <kbd
  class="mouse mod1">Left</kbd>-clicking each discreet marker, or <kbd
  class="mouse mod3">Left</kbd>-clicking the first and last markers of a range
  of markers selects them, then dragging one to a new location will move all
  selected markers together.
</p>
<p class="note">
  The markers are bounded by the zero point on
  the timeline. In other words, the first marker in your selection cannot move
  to the left of zero on the timeline.
</p>

<h2>Both ends of a range marker</h2>
<p>
  <kbd class="mod1 mouse">Left</kbd>-drag either end of the range marker. The
  other end will move by the same distance.
</p>