The following MWE doesn’t show a small capital of Ē (http://graphemica.com/Ē)
Is there no such letter with the font libertinus or how can I make it happen with LuaLaTeX?
\documentclass{scrbook}
\usepackage{fontspec}
\setsansfont[%
Numbers = {Monospaced, OldStyle},
Scale = 0.95,
]{Libertinus Sans}
\setmainfont[%
Numbers = {Monospaced, OldStyle},
Scale = 0.95,
]{Libertinus Serif}
\begin{document}
ēĒasdfjklö\textsc{asdfēĒjklö}asdfjklöēĒ
\sffamily
ēĒasdfjklö\textsc{asdfēĒjklö}asdfjklöēĒ
\end{document}
The workaround with
\usepackage{stackengine}
\newcommand\fit[3][.3ex]{\stackengine{#1}{#3}{#2}{O}{c}{F}{T}{S}}
\newcommand\macron[1]{\fit{\kern-.2ex\_}{#1}}
\newcommand\umlaut[1]{\fit{\kern-.05ex.\kern-.15ex.}{#1}}

\textsc{\=e}work? – Steven B. Segletes Sep 14 '17 at 10:20\newcommand\scmacron[1]{\fit[.2ex]{\tiny\_}{#1}}? Here, I chose\tiny, but you could pick the best size. – Steven B. Segletes Sep 14 '17 at 10:31\textsc{ē}(regular e and then U+0304 however your system allows you to input this) should work. You might want to kern it a tiny bit (eg.\textsc{e\kern-.03em̄}and/or to define a shorthand for it. – Florian Sep 14 '17 at 10:48\char{}-command built-in. – Florian Sep 14 '17 at 10:54\charobviously is available in LuaLaTeX for Unicode slots, so\textsc{e\kern-.03em\char"0304}should work just fine – Florian Sep 14 '17 at 11:15