Missing Button in UI

Hi, I don’t seem to have a button in my UI and am wondering how to enable it. Its the one in the top bar normally next to the ‘i’ info button and the viewing options.

It looks like a page with a ‘+’ on top of it.

Thanks for your help, I am reasonably new to glyphs.

We removed the button. It used to be for opening a new Edit tab. You can open a new tab by double clicking a glyph, or by pressing Cmd-T.