编辑

Question 1

standalone该解决方案为包含的文件启用目标语法tikzpicture，但在主文件中使用自定义命令。

更具体地说，conditionally是一个采用单一、强制参数的环境。

该参数应该由用于识别内容的简单标签/标记组成。
在示例中，这用作的一部分tikzpicture，但解决方案并不依赖于此。同样的机制同样可用于包含所选的引文或任意代码片段。

\flowconditional[<key-value list>]{<filename>}用于在主文档中按标签/标签选择片段<filename>。

目前仅定义了一个键，enable。
enable采用逗号分隔的值列表。
<filename>每个值应为或中的标签/标记*，其中*表示应包含所有可用代码。
然而，这一要求并非强制执行：如果传递给的值enable未在中定义filename，则该值将被默默忽略。

鉴于 OP 的图形文件名为\jobname-fig.tex，我们可以这样写

\flowconditionalpic[enable=*]{\jobname-fig}

\flowconditionalpic[enable=detour]{\jobname-fig}

\flowconditionalpic[enable={detour,longer-detour}]{\jobname-fig}

以产生目标行为。

可以使用相同的框架来包含或不包含tabular环境（尽管包含行集需要更多工作）。例如，

\begin{table}
  \caption{Tables rather than pictures}
  \flowconditional[enable=tab1]{\jobname-tab}
  \flowconditional[enable=tab2]{\jobname-tab}
\end{table}

\begin{table}
  \caption{Order is irrelevant}
  \flowconditional[enable=*]{\jobname-tab}
  \flowconditional[enable={tab2,tab1}]{\jobname-tab}
\end{table}

其中\jobname-tab.tex包含

\documentclass{standalone}
\usepackage{array}
\usepackage{booktabs}
\begin{document}
\sffamily
\begin{conditionally}{tab1}
  \begin{tabular} {ll}
    \toprule
    \bfseries Column 1 & \bfseries Column 2 \\
    \midrule
    Row 1 & Cell A \\
    \bottomrule
  \end{tabular}
\end{conditionally}
\begin{conditionally}{tab2}
  \begin{tabular} {ll}
    \toprule
    \bfseries Column 1 & \bfseries Column 2 \\
    \midrule
    Row 1 & Cell A \\
    Row 2 & Cell B \\
    \bottomrule
  \end{tabular}
\end{conditionally}
\end{document}

完整代码：

\begin{filecontents}[overwrite]{\jobname-fig.tex}
\documentclass{standalone}

\usepackage{tikz}

\begin{document}
\begin{tikzpicture}  
  \pgfmathsetmacro{\myRadius}{2} 
  \coordinate (loop-start) at (-170:\myRadius);  
  \draw[->,line width=7pt,]
  (loop-start)
  arc (-170:170:\myRadius)
  coordinate[pos=0.75] (detour-start)
  coordinate[pos=0.25] (detour-end)
  coordinate[pos=0.27] (detour-end-2)
  ;  
  \begin{conditionally}{detour}
    \draw[
    ->,
    line width=3pt,
    red,
    ] (detour-start) to[out=160, in=220, distance=6cm] (detour-end);
  \end{conditionally}  
  \begin{conditionally}{longer-detour}
    \draw[
    ->,
    line width=3pt,
    red,
    ] (detour-start) to[out=45, in=-30, distance=10cm] (detour-end-2);
  \end{conditionally}
\end{tikzpicture}
\end{document}
\end{filecontents}
\begin{filecontents}[overwrite]{\jobname-tab.tex}
\documentclass{standalone}
\usepackage{array}
\usepackage{booktabs}
\begin{document}
\sffamily
\begin{conditionally}{tab1}
  \begin{tabular} {ll}
    \toprule
    \bfseries Column 1 & \bfseries Column 2 \\
    \midrule
    Row 1 & Cell A \\
    \bottomrule
  \end{tabular}
\end{conditionally}
\begin{conditionally}{tab2}
  \begin{tabular} {ll}
    \toprule
    \bfseries Column 1 & \bfseries Column 2 \\
    \midrule
    Row 1 & Cell A \\
    Row 2 & Cell B \\
    \bottomrule
  \end{tabular}
\end{conditionally}
\end{document}
\end{filecontents}

\documentclass{article}
% ateb: https://tex.stackexchange.com/a/705487/ addaswyd o gwestiwn Flow: https://tex.stackexchange.com/q/705458/
\usepackage[subpreambles]{standalone}
\usepackage{tikz}
\ExplSyntaxOn
\bool_new:N \l_flow_condition_bool
\bool_set_false:N \l_flow_condition_bool
\keys_define:nn { flow }
{
  enable .clist_set:N = \l_flow_conditions_clist,
  enable .initial:n = ,
  enable .default:n = ,
}
\NewDocumentEnvironment { conditionally } { m +b }
{
  \clist_if_in:NnT \l_flow_conditions_clist { #1 }
  { \bool_set_true:N \l_flow_condition_bool } 
  \clist_if_in:NnT \l_flow_conditions_clist { * }
  { \bool_set_true:N \l_flow_condition_bool } 
  \bool_if:NT \l_flow_condition_bool { #2 }
}{  }
\NewDocumentCommand \flowconditional { O {} m }
{
  \group_begin:
    \keys_set:nn { flow } { #1 }
    \includestandalone { #2 }
  \group_end:
}
\ExplSyntaxOff

\begin{document}
\flowconditional[enable=*]{\jobname-fig}

\flowconditional[enable=detour]{\jobname-fig}

\flowconditional[enable={detour,longer-detour}]{\jobname-fig}


\begin{table}
  \caption{Tables rather than pictures}
  \flowconditional[enable=tab1]{\jobname-tab}
  \flowconditional[enable=tab2]{\jobname-tab}
\end{table}

\begin{table}
  \caption{Order is irrelevant}
  \flowconditional[enable=*]{\jobname-tab}
  \flowconditional[enable={tab2,tab1}]{\jobname-tab}
\end{table}

\end{document}

编辑

下面添加了一个额外的键standalone options。最初，它被设置为mode = tex。使用没有值的键将清空选项。使用有值的键将把选项设置为该值。在下面的示例中，初始值适用于大多数情况，用于angle=90演示更改选项的效果。

\documentclass{article}
% ateb: https://tex.stackexchange.com/a/705487/ addaswyd o gwestiwn Flow: https://tex.stackexchange.com/q/705458/
\usepackage[subpreambles]{standalone}
\usepackage{tikz}
\ExplSyntaxOn
\bool_new:N \l_flow_condition_bool
\bool_set_false:N \l_flow_condition_bool
\keys_define:nn { flow }
{
  enable .clist_set:N = \l_flow_conditions_clist,
  enable .initial:n = ,
  enable .default:n = ,
  standalone ~ options .tl_set:N = \l_flow_standalone_tl,
  standalone ~ options .default:n = ,
  standalone ~ options .initial:n = {mode = tex},
}
\NewDocumentEnvironment { conditionally } { m +b }
{
  \clist_if_in:NnT \l_flow_conditions_clist { #1 }
  { \bool_set_true:N \l_flow_condition_bool } 
  \clist_if_in:NnT \l_flow_conditions_clist { * }
  { \bool_set_true:N \l_flow_condition_bool } 
  \bool_if:NT \l_flow_condition_bool { #2 }
}{  }
\NewDocumentCommand \flowconditional { O {} m }
{
  \group_begin:
    \keys_set:nn { flow } { #1 }
    \flow_includestandalone:Vn \l_flow_standalone_tl { #2 }
  \group_end:
}
\cs_new_protected:Nn \flow_includestandalone:nn
{
  \includestandalone [ #1 ] { #2 }
}
\cs_generate_variant:Nn \flow_includestandalone:nn { Vn }
\ExplSyntaxOff

\begin{document}
\flowconditional[enable=*]{\jobname-fig}

\flowconditional[enable=detour,standalone options={angle=90}]{\jobname-fig}

\flowconditional[enable={detour,longer-detour}]{\jobname-fig}


\begin{table}
  \caption{Tables rather than pictures}
  \flowconditional[enable=tab1]{\jobname-tab}
  \flowconditional[enable=tab2]{\jobname-tab}
\end{table}

\begin{table}
  \caption{Order is irrelevant}
  \flowconditional[enable=*]{\jobname-tab}
  \flowconditional[enable={tab2,tab1}]{\jobname-tab}
\end{table}

\end{document}

Answer