To add a bookmark either:

• Select Sequence -> Player -> Set Bookmark at Cursor...
  The new bookmark will be appear at the cursor position on the timeline.
• Right-click the timeline at the point you wish to add a bookmark and select Set Bookmark.

The Edit Bookmark dialog will open. Enter the bookmark's name and choose the color you would like your bookmark to be by clicking the color sample, then click OK.
To check the name of a bookmark, move your mouse over it and wait until the tooltip appears.

To change the name or color of a bookmark, right-click it and select Edit Bookmark... The Edit Bookmark dialog will open.

To remove a bookmark, right-click it and select Remove Bookmark.

You can move the timeline position to match any created bookmark on a sequence by selecting the bookmark from Sequence -> Player -> Goto Bookmark... -> Bookmark-Name
Bookmarks in this list will be ordered sequentially as they appear in the sequence.