Yes, I use Ctrl+Space. "add" wasn't there when I tried. I just tried it again and see that "add" has been added, as well as "append" and one or two others. For example, I just discovered "refresh_header" (which I needed to refresh the score in the header prior to "end_game"), but "set_string" is still not there. I worked this one out by trial and error.
Note that Ctrl+Space is very dicky. For me, it mostly only works on a new line, it doesn't work when you've got a syntax error and the hint suggestions (as shown in your tutorial videos) don't work for me at all.
Is there a master list of all the commands anywhere? At one point I had a syntax error and when I hovered over the error icon in the left margin, the tool tip showed hundreds of suggestions - so many, in fact, that they wouldn't all fit on the screen.