User blog comment:Kirkburn/Technical Update: July 1, 2015/@comment-3388044-20150704060938/@comment-452-20150705141309

There is nothing to "remember", there are 2 buttons:
 * A button to select the "Desktop" option
 * A button to select the "Mobile" option

I'll try explaining this in more detail:

In other words:
 * When you press the "Mobile" button, you get the "Mobile" option.
 * When you press the "Desktop" button, you get the "Desktop" option.
 * There is no "Desktop XL" button.
 * There is no "Tablet Portrait" button.

I've said elsewhere that I think it would be best for them to should change it to have 4 preview buttons: one for each option. However, I'm personally glad that they haven't, and personally hope that they won't, as it would require me to make further adjustments to my edit bar.

Can you please confirm that the "It used to be" you're referring to was when there was only one button?