need to track # of times a video is opened/viewed on a Samsung Galaxy tablet. How?
You can use Android secret code *#*#4636#*#* to track the usage time of the video player. While that does not give you the number of times video player has been opened, it should give you a fair indicator of the number of times (= usage / video duration ). The secret code needs to be entered on the dialpad of your telephone app

This app does the same and is an alternate to the secret code - 4636. Screenshot of usage time on my device below. You have options to track usage as shown

( Thanks to OP for highlighting another app App Usage that worked but 4636 didn't)