Put an X on the tile in the tileset in the database. If that doesn't work you either set the player to through ON (via a move route), or accidentally set the first tile in B on that tileset to anything but star.
I've noticed that more videos on YouTube have these segmented bookmark things in the videos themselves. It's nice being able to jump to parts of a video you want, and to have them all clearly labelled.
I've always dreaded planning for my games so I just didn't plan at all. That... didn't work out after all.
Turns out it can be kind of fun if you keep the scope small and don't take it way too seriously.