Here is how to make a Thumbnail in Scratch of 2020. First… Make a sprite to be your thumbnail. Then when you do that, put a simple script.

Then after that script was followed, You then have a complete Thumbnail! Click the stop sign on your project and you'll see the thumbnail.

*the go to front block needs to be added so any other sprites does not get in the way of the thumbnail when it is not supposed to.*

THANK YOU SO FREAKING MUCH

Thanks!

TYSM