i found it in the "Edit/Settings" tab
This is not quite the same thing as using Bookmarks. However, if it works for you all's good.
Enabling the start time and end time in the Edit/Settings tab results in only this section of the track being played whenever the track is played.
I don't believe there is any way of using the wave bar to set these start and end times (although I admit that I have rarely used this setting so I may be wrong).
If you use Bookmarks, you can play the whole track in the usual way, or you can play the section of the track as defined by the bookmark start and end times (by playing the bookmark in the bookmarks node).
Also, you can set the start and end times by pausing a track, click on the wave bar and CTRL-D (sets start time) and then clicking on the next position on the wave bar and CTRL-D (sets end time).