编辑：

Question

至于带有文字的箭头0.5，可以通过node {$0.5$}在路径内添加来实现。它看起来像这样

\draw [->] (plus.south east) -- node[anchor=south west]{$0.5$} (c2.north);

另外两个要点可以通过两种方式解决：

无需对您的确切代码进行任何具体更改，通过添加local bounding box到外部平行四边形，您可以随后调用它并将其视为节点。

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{graphicx}
\usepackage{float}
\usepackage{amsmath}
\usepackage{amsthm}
\usepackage{tikz}
\usetikzlibrary{chains,shapes.multipart}
\usetikzlibrary{shapes, fit}
\usetikzlibrary{automata,positioning}
\usetikzlibrary{intersections}



\tikzset{
    activity/.style={
        draw,
        rectangle,
        minimum height = 0.8cm,
        minimum width = 1.5cm
    },
}

\begin{document}

\begin{tikzpicture}
% Outer parallelogram (TaskA)
\draw[local bounding box=pOA] (0,0) -- (-100:6cm) --++ (0:6cm) --++ (80:6cm) -- (0,0);
\node at (5,-0.5) {TaskA};

% Inner parallelogram (EntryA)
\draw (1.5,0) --++ (-100:1cm) --++ (0:2cm) --++ (80:1cm);
\node at (2.3,-0.5) {EntryA};

% Activities 
\node[activity] (s) at (2.3,-2) {source};
\node[circle, draw] (plus) at (2.3, -3.5) {+};
\node[activity] (c1) at (1, -5) {choice1};
\node[activity] (c2) at (3.6, -5) {choice2};

\draw [->] (2.3,-1) -- (s.north);
\draw [->] (s.south) -- (plus.north);
\draw [->] (plus.south east) -- node[anchor=south west]{$0.5$} (c2.north);
\draw [->] (plus.south west) -- node[anchor=south east]{$0.5$} (c1.north);



% TaskB
\draw[local bounding box=pOB] (0,-8) --++ (-100:2cm) --++ (0:6cm) --++ (80:2cm) -- (0,-8);
\node at (2.8,-9.5) {TaskB};

% EntryB1
\draw[local bounding box=e1] (0.5,-8) --++ (-100:1cm) --++ (0:2cm) --++ (80:1cm);
\node (eB1) at (1.3,-8.5) {EntryB1};

% EntryB2
\draw[local bounding box=e2] (3.5,-8) --++ (-100:1cm) --++ (0:2cm) --++ (80:1cm);
\node (eB2) at (4.3,-8.5) {EntryB2};

\node[circle,draw] (pA) at (8, -5) {ProcA};
\node[circle,draw] (pB) at (8, -10) {ProcB};

\draw [->] (c1.south) -- (e1.north);
\draw [->] (c2.south) -- (e2.north);

\draw [->, shorten <= -18pt] (pOA.east) -- (pA);
\draw [->, shorten <= -5pt] (pOB.east) -- (pB);


\end{tikzpicture}

\end{document}

但是，local bounding box会创建一个矩形框，因此，为了使箭头指向外部平行四边形，您需要使用shorten <=并目测长度以使其看起来像实际连接

我个人建议的第二种方法不存在目测问题。它使用shapes库以及fit一个库。它们显然都已加载。这样，您不再需要使用路径创建平行四边形，而是使用节点形状。这样，您可以像平常一样简单地绘制箭头，它们将像应该的那样连接起来。

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{graphicx}
\usepackage{float}
\usepackage{amsmath}
\usepackage{amsthm}
\usepackage{tikz}
\usetikzlibrary{chains,shapes.multipart}
\usetikzlibrary{shapes, fit}
\usetikzlibrary{automata,positioning}


\begin{document}

\begin{tikzpicture}[
every node/.style={draw, inner sep=8pt},
parallelogram/.style={draw, trapezium, trapezium left angle=80, trapezium right angle=-80}
]

% Outer parallelogram (TaskA)
\node[draw=none] (tA) at (5,-0.5) {TaskA};

\node[parallelogram] (eA) at (2.3,-0.5) {EntryA};

% Activities 
\node (s) at (2.3,-2) {source};
\node[circle] (plus) at (2.3, -3.5) {+};
\node (c1) at (1, -5) {choice1};
\node (c2) at (3.6, -5) {choice2};

\draw [->] (eA) -- (s.north);
\draw [->] (s.south) -- (plus.north);
\draw [->] (plus.south east) -- node[draw=none, inner sep=1pt, anchor=south west]{$0.5$} (c2.north);
\draw [->] (plus.south west) -- node[draw=none, inner sep=1pt, anchor=south east]{$0.5$} (c1.north);

% TaskB
\node[draw=none] (tB) at (2.8,-9.5) {TaskB};

% EntryB1
\node[parallelogram] (eB1) at (1.3,-8.5) {EntryB1};

% EntryB2
\node[parallelogram] (eB2) at (4.3,-8.5) {EntryB2};

\node[circle, inner sep=2pt] (pA) at (8, -5) {ProcA};
\node[circle, inner sep=2pt] (pB) at (8, -10) {ProcB};

\draw[->] (c1.south) -- (eB1.north);
\draw[->] (c2.south) -- (eB2.north);

\node[parallelogram, xshift=10pt, fit=(eA) (c1) (c2)] (pOA) {};

\node[parallelogram, fit=(eB1) (eB2) (tB)] (pOB) {};

\draw[->] (pOA) -- (pA);
\draw[->] (pOB) -- (pB);

\end{tikzpicture}

\end{document}

编辑：

关于评论中讨论的顶部对齐。

对于第二种方法，外平行四边形是使用fittikz 库创建的节点，基本上会创建一个适合所有列出内容的节点。由于它是一个节点，因此可以通过inner sep选项设置填充。但是，没有办法只控制一侧（左、右、上、下），因此为了实现该效果，您可以按填充量填充节点并获得所需的对齐方式。

由于innner sep可以在您决定的任何时候更改，因此也必须修改移位。虽然有一种更通用的方法可以做到这一点，但使用\pgfkeysvalueof{/pgf/inner ysep}它提取当前填充，以便移位将根据更改自动更新inner sep

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{graphicx}
\usepackage{float}
\usepackage{amsmath}
\usepackage{amsthm}
\usepackage{tikz}
\usetikzlibrary{chains,shapes.multipart}
\usetikzlibrary{shapes, fit}
\usetikzlibrary{automata,positioning}


\begin{document}

\begin{tikzpicture}[
every node/.style={draw, inner sep=8pt},
parallelogram/.style={draw, trapezium, trapezium left angle=80, trapezium right angle=-80}
]

% Outer parallelogram (TaskA)
\node[draw=none] (tA) at (5,-0.5) {TaskA};

\node[parallelogram] (eA) at (2.3,-0.5) {EntryA};

% Activities 
\node (s) at (2.3,-2) {source};
\node[circle] (plus) at (2.3, -3.5) {+};
\node (c1) at (1, -5) {choice1};
\node (c2) at (3.6, -5) {choice2};

\draw [->] (eA) -- (s.north);
\draw [->] (s.south) -- (plus.north);
\draw [->] (plus.south east) -- node[draw=none, inner sep=1pt, anchor=south west]{$0.5$} (c2.north);
\draw [->] (plus.south west) -- node[draw=none, inner sep=1pt, anchor=south east]{$0.5$} (c1.north);

% TaskB
\node[draw=none] (tB) at (2.8,-9.5) {TaskB};

% EntryB1
\node[parallelogram] (eB1) at (1.3,-8.5) {EntryB1};

% EntryB2
\node[parallelogram] (eB2) at (4.3,-8.5) {EntryB2};

\node[circle, inner sep=2pt] (pA) at (8, -5) {ProcA};
\node[circle, inner sep=2pt] (pB) at (8, -10) {ProcB};

\draw[->] (c1.south) -- (eB1.north);
\draw[->] (c2.south) -- (eB2.north);

\node[parallelogram, xshift=10pt, yshift=-\pgfkeysvalueof{/pgf/inner ysep}, fit=(eA) (c1) (c2)] (pOA) {};

\node[parallelogram, inner ysep=3pt, xshift=-3pt, yshift=-\pgfkeysvalueof{/pgf/inner ysep}, fit=(eB1) (eB2) (tB)] (pOB) {};

\draw[->] (pOA) -- (pA);
\draw[->] (pOB) -- (pB);

\end{tikzpicture}

\end{document}

Answer 1