\documentclass[a4paper,12pt]{book}
\usepackage{cxltx-style-accentbox}
\begin{document}

{
\textit{Some variations with an asterisk placed above an `i':}
i\upaccent{\tiny *}{\i}i\upaccent{\tiny *}{\i}i\upaccent{\tiny *}{\i}
\textit{i\upaccent{\tiny *}{\i}i\upaccent{\tiny *}{\i}i\upaccent{\tiny *}{\i}}
}

ab\upaccent{w}{c}de
ab\upaccent{\tiny w}{c}de
ab\upaccent{\tiny s}{\upaccent{\tiny w}{c}}de

\end{document}