\tex_scantokens D:

\documentclass{article}
\usepackage{filecontentsdef}[2019/04/20]
\usepackage{xparse}
\usepackage{fvextra}
\usepackage{newvbtm}
\setlength{\parindent}{0pt} % just for the example
\ExplSyntaxOn
\tl_new:N \l__scontents_macro_tmp_tl
\keys_define:nn { scontents }
  {
    save-env  .tl_set:N   = \l__scontents_name_seq_tl,
    save-env  .initial:n  = contents,
    show-env  .bool_set:N = \l__scontents_show_env_bool,
    show-env  .initial:n  = false
  }
% Adapted from https://tex.stackexchange.com/a/215571/7832
\cs_new_protected:Npn \__scontents_append_contents:nn #1#2
  {
    \seq_if_exist:cF { g__scontents_seq_name_#1_seq }
      { \seq_new:c { g__scontents_seq_name_#1_seq } }
    \seq_gput_right:cn { g__scontents_seq_name_#1_seq } {#2}
  }
\cs_new_protected:Npn \__scontents_getfrom_seq:nn #1#2
  { \seq_item:cn { g__scontents_seq_name_#2_seq } {#1} }
\NewExpandableDocumentCommand { \getstored } { O{1} m }
  { \__scontents_getfrom_seq:nn {#1} {#2} }
% Define scontents (wrap \filecontentsdefmacro) whit [key=val] Delaying
% Adapted from https://tex.stackexchange.com/a/487746/7832
\NewDocumentEnvironment { scontents } { }
  {
    \char_set_catcode_active:N \^^M
    \scontents_start_environment:w
  }
  {
    \scontents_stop_environment:
    \scontents_atend_environment:
  }
\cs_new_protected:Npn \scontents_environment_keys:w [ #1 ]
  { \keys_set:nn { scontents } {#1} }
\group_begin:
  \char_set_catcode_active:N \^^M
  \cs_new_protected:Npn \scontents_start_environment:w #1 ^^M
    {
      \tl_if_blank:nF {#1} { \scontents_environment_keys:w #1 }
      \group_begin: % open group for env
        \filecontentsdefmacro { \l__scontents_macro_tmp_tl } ^^M
    }
  \cs_new_protected:Nn \scontents_stop_environment:
    {
        \endfilecontentsdefmacro
      \group_end: % close group for env
    }
\group_end:
\cs_gset_protected:Nn \__scontents_macro_to_seq:
  {
    \regex_replace_all:nnN { \^^M } { \^^J } \l__scontents_macro_tmp_tl
    \cs_log:N \l__scontents_macro_tmp_tl
    \exp_args:NNx \__scontents_append_contents:nn \l__scontents_name_seq_tl
      { \exp_not:N \tex_scantokens:D { \tl_use:N \l__scontents_macro_tmp_tl } }
  }
% Code after scontent environment \seq_item:cn { g__scontents_seq_name_#2_seq } { #1 }
\cs_new_protected:Nn \scontents_atend_environment:
  {
    \__scontents_macro_to_seq:
    \bool_if:NT \l__scontents_show_env_bool
      { \__scontents_getfrom_seq:nn { -1 } { \l__scontents_name_seq_tl } }
    \tl_clear:N \l__scontents_macro_tmp_tl
  }
% \newverbatim{typescverb}{}{}{}{}
\DefineVerbatimEnvironment{typescverb}{Verbatim}{}
\cs_new_eq:Nc \__scontents_fcdef_get:NN { filecontentsdef@get }
\cs_new:Npn \__scontents_strip_scantokens:N #1
  { \exp_args:NV \__scontents_strip_scantokens:n #1 }
\cs_new:Npn \__scontents_strip_scantokens:n #1
  { \exp_not:o { \use_ii:nn #1 } }
\group_begin:
  \char_set_catcode_active:N \^^M
  \cs_new:Npn \__scontents_fcdef_print:N #1
    {
      \cs_set_eq:NN \__scontents_fcdef_saved_EOL: ^^M
      \cs_set_eq:NN ^^M \scan_stop:
      \use:x
        {
          \exp_not:N \tex_scantokens:D
            {
              \exp_not:N \begin{typescverb} ^^M
              \__scontents_strip_scantokens:N #1
              \c_backslash_str end \c_left_brace_str typescverb \c_right_brace_str ^^M
            }
        }
      \cs_set_eq:NN ^^M \__scontents_fcdef_saved_EOL:
    }
\group_end:
\NewDocumentCommand { \typestored } { O{1} m }
  {
    \group_begin:
    \tl_put_right:Nx \l_tmpb_tl
      { \seq_item:cn { g__scontents_seq_name_#2_seq } {#1} }
    \__scontents_fcdef_get:NN \__scontents_fcdef_print:N \l_tmpb_tl
    \group_end:
  }
\ExplSyntaxOff
\begin{document}

\section*{Test environment}
Test \verb+\begin{scontents}+ no \verb+[key=val]+\par

\begin{scontents}
Using \verb+scontents+ env no \verb+[key=val]+, save in \verb+contents+
with index $1$\footnote{AND footnotes !!}.%

Prove new \Verb*{ new fvextra whit braces } and environment \verb+Verbatim+

\begin{Verbatim}
(A) verbatim environment                                               %
many space here and percent at end of line                             %
                                many space
\end{Verbatim}
No espace after, see \verb+https://tex.stackexchange.com/a/460967/7832+.\par
Use \verb|\relax|.\relax
\end{scontents}

\section*{Show stored contents}
XX\getstored[1]{contents}NO space here :)\par

\section*{typestored}
\typestored[1]{contents} % not work
\end{document}