You can restrict the viewer's ability to click to different points on the progress bar through Settings -> Customization.
Allow or disallow seeking in the progress bar
- After signing in, click the Settings button for the video you wish to modify.
- In the Settings submenu, choose Customization.
- Under Seeking check the box beside Allow Seeking to allow the viewer to use the progress bar freely or uncheck it to disallow it.
- Click Save.