If you need to use Bookmark/s in VLC, this is one way you can do it.
For example, to quit viewing in the middle of a video and resume viewing that video exactly where you left off - much later, after viewing other videos during the intervening period.

View the video in VLC.
Press Ctrl-B to manage bookmarks.
Click on Create.
Then it will make a bookmark at that particular point in the video.
Click on X or Close the dialogue box.
Then Press Ctrl-Y to save the playlist to file.
You can type in the name of the playlist.
It will save playlist in same folder as the video.
The bookmark will be saved into the playlist file.

The next time you play the playlist, the bookmark is intact.
If you did not save playlist to file, the bookmark is gone the next time you play the same video.

To test it out, exit from VLC.

Run VLC again.
Click on Open File.
Click on the name of the playlist that you saved.

The video plays.

Go to main menu, Click on Playback
A scroll down list appears.
Click on Custom Bookmarks.
A scroll list appears. It says on the top, Custom Bookmarks - Ctrl B.
And beneath that, is the saved Bookmark that you want to jump to and resume watching the video.

You just click on the bookmark that you saved
It will jump to the bookmarked point where you left off and you can resume viewing.


Special Note:

Do NOT Press Ctrl-B to search for the saved Bookmark.
The manage bookmark dialogue box is shown.
But it is completely empty.
This has deluded many users into thinking that VLC never saved the Bookmark.

This is an idiosyncrasy of VLC.
Ctrl-B merely calls up the "Create Bookmark" dialogue box.
It does not display any previously saved Bookmark.

But if you use the main menu Playback and submenu Custom Bookmarks, the saved Bookmark will be shown.

In case you are wondering, the saved playlist file with the saved Bookmark is very small in size. It does not recopy the entire video. It only saves the instructions of what video to play and where the saved Bookmarks are within it.