I was today years old when I learned how to change the thumbnail on a YouTube Short using my phone.
First. YouTube is retarded. Why can't I simply do that on the desktop or in the YT StudioApp?
Anyway, here is how you do it in 10 steps:
1. Open the YouTube app (not YouTube Studio).
2. Tap your channel logo in the top-right corner.
3. Select "Your videos" from the menu.
4. Find the Short you want to edit.
5. Tap the three dots on the right-hand side of the video.
6. From the dropdown menu, select "Edit" (pencil icon).
7. The video will appear at the top of your screen.
8. Tap the pencil icon on the video thumbnail.
9. At the bottom of the screen, a rectangle slider will appear.
10. Drag it to choose the frame you want as the new thumbnail. Once you're happy with your choice, tap "Save" at the top.
And just like that, it’s done! 🎉