Macros that define other macros, which also define other macros

As I mentioned in a comment, neither a hyphen nor a numeral can be used when constructing macro names unless you will always write the equivalent of \csname ... \endcsname or ensure the catcodes are changed when using them.

Hence, it is necessary to modify the user interface from that suggested.

The basic idea seems to be to create a series of indexed lists of argument which can be retrieved by giving the name of the list and the index of the item within that list.

This could be implemented using comma-separated lists. Here is a suggested interface which uses only expl3 syntax considered stable by the developers:

\buildmacro{<list identifier>}
\addmacro{<list identifier>}{<item to be added>}
\fetchmacro{<list identifier>}{<index of item to be fetched>}
\listmacro{<list identifier>}

The first sets things up by initialising a new list. The second adds an item to a list. The third fetches an item from a list. The fourth lists all items in a list sequentially.

Proof of concept (though hardly an original one):

\documentclass{article}
\usepackage{xparse}
\ExplSyntaxOn
\cs_new_protected_nopar:Nn \digitalink_buildmacro:n
{
  \clist_new:c { g_digitalink_#1_clist }
}
\NewDocumentCommand \buildmacro { m }
{
  \digitalink_buildmacro:n { #1 }
}
\NewDocumentCommand \addmacro { m +m }
{
  \clist_gput_right:cn { g_digitalink_#1_clist }
  {
    #2
  }
}
\NewDocumentCommand \fetchmacro { m m }
{
  \clist_item:cn { g_digitalink_#1_clist } { #2 }
}
\NewDocumentCommand \listmacro { m }
{
  \clist_use:cn { g_digitalink_#1_clist } { \par }
}
\ExplSyntaxOff
\begin{document}
\buildmacro{dititle}
\addmacro{dititle}{Here's some text.}
\addmacro{dititle}{Here's some more.}
\fetchmacro{dititle}{1}
\fetchmacro{dititle}{2}
\fetchmacro{dititle}{1}

List:

\listmacro{dititle}
\end{document}

From the description of the flow required this seems quite simple

\newcommand\buildmacro[1]{%
  % Create a new counter named after the argument
  \newcounter{#1Xcounter}%
  % Create a new command named after the argument,
  % itself taking one argument
  \expandafter\newcommand\csname #1\endcsname[1]{%
    % Step the counter
    \stepcounter(#1Xcounter)%
    % Store the argument
    \expandafter\newcommand\csname #1-\arabic{#1Xcounter}\endcsname
      {##1}%
  }%
}

As a plain version was also requested

\long\def\buildmacro#1{%
  \csname newcount\expandafter\endcsname\csname #1Xcounter\endcsname
  \long\expandafter\def\csname #1\endcsname##1{%
    \global\expandafter\advance\csname #1Xcounter\endcsname by 1
    \expandafter\def\csname #1-\expandafter\number\csname #1Xcounter\endcsname
      \endcsname
      {##1}%
  }%
}

A \@namedef and \@nameuse version, faking 'macro' names that would not be possible without catcode change.

The allocation of \newcounter inside of macros may cause troubles with counter registers.

\documentclass{article}

\makeatletter
\newcommand{\buildmacro}[1]{%
  \newcounter{#1Xcounter}%
    \expandafter\newcommand\csname #1\endcsname[1]{%
      \stepcounter{#1Xcounter}%
      \@namedef{#1-\number\value{#1Xcounter}}{##1}%
  }
}

\newcommand{\displaymacrocontent}[2]{%
  \@nameuse{#1-#2}%
}
\makeatother



\begin{document}

\buildmacro{Title}
\Title{The first title}
\Title{The second title}
\Title{The third title}

\newcount\tmpcntr

\loop\unless\ifnum\tmpcntr > 4
\advance\tmpcntr by 1
\displaymacrocontent{Title}{\number\tmpcntr}

\repeat



\end{document}