Per feedback at mw.org:
ManosHacker writes,
"References list" is inserted, out of new users' logic or expectation, by a well hidden button, away from "Cite" button.
"References list" insertion button could be appearing below "Cite" button, while hovering over it. A tooltip would be much appreciated.
At the moment with Citoid enabled there is no cite menu, just a button. It's certainly going to be used a lot less than Cite (only on page creation) so doesn't make sense to give it the same prominence.
Per Ed; a better solution to this issue will be T56906: Append a references list to bottom of the page when the first reference is added.