Here is a link to a Janome video with tips and tricks about the start/stop button. I never really used the start/stop except with embroidery, but at a retreat my foot petal would not stay put and I got tired of chasing it around, so switched to the button and was pleased with how easy it is to use. Always good to have another option, no matter what!
If you have a Janome machine, this series of videos on "tips and tricks" are pretty informative. Not familiar with other brands but the basic info may be helpful with them too.
https://www.youtube.com/watch?v=27bHw0gaRGY