Generate thumbnail option from video

Hello everyone,
There are currently two ways to have thumbnails in the video.

  1. Automatically randomly generate the thumbnail.
  2. Manuall upload the thumbnail on video setting.

For instance assume I am uploading a video of a Educational Lecture.
With random thumbnail it may create some confusion.
So, I want to specify a specific time to use as thumbnail from the video.
Like in 4mins long video (Use 03:15 as my thumbnail).
Currently, Youtube provides the option to show as Thumbnail as shown below: