Math mode accents
Choose the one you like:
% arara: lualatex
\documentclass{article}
\usepackage{unicode-math}
\usepackage{mathtools}
\setmathfont{XITS math}
\begin{document}
Accents above:
\begin{itemize}
\item \verb+\grave+ $\grave x\quad Z_{\grave x}\quad Z_{Z_{\grave x}}$
\item \verb+\acute+ $\acute x\quad Z_{\acute x}\quad Z_{Z_{\acute x}}$
\item \verb+\hat+ $\hat x\quad Z_{\hat x}\quad Z_{Z_{\hat x}}$
\item \verb+\widehat+ $\widehat x\quad Z_{\widehat x}\quad Z_{Z_{\widehat x}}$
\item \verb+\tilde+ $\tilde x\quad Z_{\tilde x}\quad Z_{Z_{\tilde x}}$
\item \verb+\bar+ $\bar x\quad Z_{\bar x}\quad Z_{Z_{\bar x}}$
\item \verb+\overbar+ $\overbar x\quad Z_{\overbar x}\quad Z_{Z_{\overbar x}}$
\item \verb+\overline+ $\overline x\quad Z_{\overline x}\quad Z_{Z_{\overline x}}$
\item \verb+\breve+ $\breve x\quad Z_{\breve x}\quad Z_{Z_{\breve x}}$
\item \verb+\dot+ $\dot x\quad Z_{\dot x}\quad Z_{Z_{\dot x}}$
\item \verb+\ddot+ $\ddot x\quad Z_{\ddot x}\quad Z_{Z_{\ddot x}}$
\item \verb+\ovhook+ $\ovhook x\quad Z_{\ovhook x}\quad Z_{Z_{\ovhook x}}$
\item \verb+\ocirc+ $\ocirc x\quad Z_{\ocirc x}\quad Z_{Z_{\ocirc x}}$
\item \verb+\check+ $\check x\quad Z_{\check x}\quad Z_{Z_{\check x}}$
\item \verb+\candra+ $\candra x\quad Z_{\candra x}\quad Z_{Z_{\candra x}}$
\item \verb+\oturnedcomma+ $\oturnedcomma x\quad Z_{\oturnedcomma x}\quad Z_{Z_{\oturnedcomma x}}$
\item \verb+\ocommatopright+ $\ocommatopright x\quad Z_{\ocommatopright x}\quad Z_{Z_{\ocommatopright x}}$
\item \verb+\droang+ $\droang x\quad Z_{\droang x}\quad Z_{Z_{\droang x}}$
\item \verb+\leftharpoonaccent+ $\leftharpoonaccent x\quad Z_{\leftharpoonaccent x}\quad Z_{Z_{\leftharpoonaccent x}}$
\item \verb+\rightharpoonaccent+ $\rightharpoonaccent x\quad Z_{\rightharpoonaccent x}\quad Z_{Z_{\rightharpoonaccent x}}$
\item \verb+\overleftarrow+ $\overleftarrow x\quad Z_{\overleftarrow x}\quad Z_{Z_{\overleftarrow x}}$
\item \verb+\vec+ $\vec x\quad Z_{\vec x}\quad Z_{Z_{\vec x}}$
\item \verb+\dddot+ $\dddot x\quad Z_{\dddot x}\quad Z_{Z_{\dddot x}}$
\item \verb+\ddddot+ $\ddddot x\quad Z_{\ddddot x}\quad Z_{Z_{\ddddot x}}$
\item \verb+\overleftrightarrow+ $\overleftrightarrow x\quad Z_{\overleftrightarrow x}\quad Z_{Z_{\overleftrightarrow x}}$
\item \verb+\annuity+ $\annuity x\quad Z_{\annuity x}\quad Z_{Z_{\annuity x}}$
\item \verb+\widebridgeabove+ $\widebridgeabove x\quad Z_{\widebridgeabove x}\quad Z_{Z_{\widebridgeabove x}}$
\item \verb+\asteraccent+ $\asteraccent x\quad Z_{\asteraccent x}\quad Z_{Z_{\asteraccent x}}$
\end{itemize}
Accents below:
\begin{itemize}
\item \verb+\wideutilde+ $\wideutilde x\quad Z_{\wideutilde x}\quad Z_{Z_{\wideutilde x}}$
\item \verb+\underbar+ $\underbar x\quad Z_{\underbar x}\quad Z_{Z_{\underbar x}}$
\item \verb+\underline+ $\underline x\quad Z_{\underline x}\quad Z_{Z_{\underline x}}$
\item \verb+\threeunderdot+ $\threeunderdot x\quad Z_{\threeunderdot x}\quad Z_{Z_{\threeunderdot x}}$
\item \verb+\underrightharpoondown+ $\underrightharpoondown x\quad Z_{\underrightharpoondown x}\quad Z_{Z_{\underrightharpoondown x}}$
\item \verb+\underleftharpoondown+ $\underleftharpoondown x\quad Z_{\underleftharpoondown x}\quad Z_{Z_{\underleftharpoondown x}}$
\item \verb+\underleftarrow+ $\underleftarrow x\quad Z_{\underleftarrow x}\quad Z_{Z_{\underleftarrow x}}$
\item \verb+\underrightarrow+ $\underrightarrow x\quad Z_{\underrightarrow x}\quad Z_{Z_{\underrightarrow x}}$
\item \verb+\underline+ $\underline x\quad Z_{\underline x}\quad Z_{Z_{\underline x}}$
\end{itemize}
Trailing signs (could be set as subscript or prescripts as well:
\begin{itemize}
\item \verb+^\prime+ $x^\prime\quad Z_{x^\prime}\quad Z_{Z_{x^\prime}}$
\item \verb+^\dprime+ $x^\dprime\quad Z_{x^\dprime}\quad Z_{Z_{x^\dprime}}$
\item \verb+^\trprime+ $x^\trprime\quad Z_{x^\trprime}\quad Z_{Z_{x^\trprime}}$
\item \verb+^\qprime+ $x^\qprime\quad Z_{x^\qprime}\quad Z_{Z_{x^\qprime}}$
\item \verb+^\backprime+ $x^\backprime\quad Z_{x^\backprime}\quad Z_{Z_{x^\backprime}}$
\item \verb+^\backdprime+ $x^\backdprime\quad Z_{x^\backdprime}\quad Z_{Z_{x^\backdprime}}$
\item \verb+^\backtrprime+ $x^\backtrprime\quad Z_{x^\backtrprime}\quad Z_{Z_{x^\backtrprime}}$
\item \verb+^\hyphenbullet+ $x^\hyphenbullet\quad Z_{x^\hyphenbullet}\quad Z_{Z_{x^\hyphenbullet}}$
\item \verb+^\ast+ $x^\ast\quad Z_{x^\ast}\quad Z_{Z_{x^\ast}}$
\item \verb+^\vysmwhtcircle+ $x^\vysmwhtcircle\quad Z_{x^\vysmwhtcircle}\quad Z_{Z_{x^\vysmwhtcircle}}$
\item \verb+^\vysmblkcircle+ $x^\vysmblkcircle\quad Z_{x^\vysmblkcircle}\quad Z_{Z_{x^\vysmblkcircle}}$
\item \verb+^\llcorner+ $x^\llcorner\quad Z_{x^\llcorner}\quad Z_{Z_{x^\llcorner}}$
\item \verb+^\ulcorner+ $x^\ulcorner\quad Z_{x^\ulcorner}\quad Z_{Z_{x^\ulcorner}}$
\end{itemize}
\end{document}
While you can do this, I'd revise my notation. If you have the same base symbol with so many variants to distinguish, your gentle reader will soon be utterly confused. Check what is standard in the area, or at least what are common alternatives. Consider using different base fonts for different concepts (e.g. I use $a_n$ for elements of a sequence, $A(z)$ and $\widehat{A}(z)$ for respective generating functions, $\mathcal{A}$ for sets; use greek letters for strings, ...).
I had the same problem with the actuarial symbol and the subscript/superscript. I made a package who can help for some of the notation describe.
Plus, I’ve add some shortcut to save time. Like the double dot symbol, multiple subscript, etc.
The GitLab : https://vigou3.gitlab.io/actuarialsymbol/
And the CTAN : http://ctan.org/pkg/actuarialsymbol
All you need is the actuarialsymbol package.
At the beginning of the code you have to write
\usepackage{actuarialsymbol}
For the sub/superscript
\actsymb['subscripLeft']['superscriptL']{<middle>}{'subscriptR'}{'superscriptR'}
Example of output:
I try to be consequent with the quality of the alignment.
Example of shortcut for actuarial symbol :