manual/include/creating-location-markers.html

<p>
  <dfn>Location Markers</dfn> appear in the <dfn>Locations ruler</dfn> at the top
  of the timeline. The <dfn>begin</dfn> and <dfn>end</dfn> markers appear
  automatically, but you can create custom markers at any position in a
  session.
</p>
<p>
  To add a marker at the <strong>current playhead position</strong>, press
  <kbd>Num-&crarr;</kbd> (the Enter key on the numeric  keypad).
  Alternatively, use <kbd class="menu">Transport &gt; Markers &gt; Add
  Mark from Playhead</kbd>.
</p>
<p>
  To add a marker at an <strong>arbitrary location</strong> on the timeline,
  navigate to the desired position, right-click on the Locations ruler and
  select <kbd class="menu">New Location Marker</kbd>.
  You can also go to the Editor list, click <kbd class="menu">New
  Marker</kbd> and use the clock widget to set its position.
</p>
<p>
  For details see
  <a href="@@the-ranges-and-marks-lists">Ranges &amp; Marks List</a>
  and <a href="@@editing-clocks">Editing Clocks</a>.
</p>