+1 for Magic Citations tool again. If not, at least support for Pages, Ulysses and Manuscripts.io
Are smart cite and citekeys available on PAGES 5.6.7 on mac OS el capitan?
Yes. The new SmartCite for Citekeys works with Pages as long as you save the document as a .docx.
Smartcite to insert /cite in Latex just like Magic citation in papers 3.