I know you included a link to a list of tutorials but for those who don’t want to search: you just click, hold, and the edges of the color. If you click, hold, and move anywhere else it selects.
I found it. When you see your palette with all the color that you’ve choice, you only have to click on the color espacially and then your color will be surrounded by a light yellow square. You only have to click and hold on the yellow square and you’ll be able to move it