Missing Plus Button to add screen sizes

Hi,

It seems like the plus icon that is used to add various screen sizes have disappeared from my canvas.

I can’t figure out why this is happening, is this because I am in free tier?

Thank you in advance.

Ah sorry, I actually found it.
For anyone wondering, there is a design mode that you can toggle by pressing M, or from View (menu bar) → Turn on/off Design mode.

The multiple screens is only visible in design mode.