How to draw a tikz list environment as a show in the picture

Question

I want to create a tikz list environment, as shown in the figure. So that the vertical space is flexible when x, y, z and w are fractions or drawings.

example

Answer 1

As Torbjørn T. said in the comments matrices are most likely the way to go (especially when considering that there's drawings to made in the "itemize" environment). But I thought it would be nice to implement this so called itemize in an itemize manner. With that being said, we need a complient \item, also, unfortunately, my skills with LaTeX does not allow me to deal with a pagebreaking system, if someone thinks it's a nice idea, they're welcome to it :)!

The counter can be adjusted in the old fashion way, The label image is made with a node shape which must receive an argument, being that the node name (for drawing the background afterwards. Furthermore, the separation between the label image and label number can be set with label sep and the separation between item entry and label number with numlabel sep. Since in a matrix of nodes when the parser encounters a \path command it does not wrap the contents in a \node{ } and then we can draw as if we were on a tikzpicture, where the origin of the CS is the baseline, that being said we can do something like:

    \begin{myitemize}[%
        myitem label style={fill=black,yshift=.2mm},
        label background={draw, gray, line width=1.2em, shorten <=-2mm}]
        \item $\dfrac{1}{2}$\\
        \item \draw[scale=0.5] (4,-1.5) node[shift={(-20:-.5)}, centered]{$\theta$} -| coordinate[pos=.5](rect) node[pos=.25, below]{4} node[pos=.75,left](tmp){3} ++(-4,3) -- cycle;
              \draw (rect) rectangle node[circle, fill=black, inner sep=0pt, minimum size=1.5pt, centered]{} ++(.2,.2);\\
        \item Something else\\
    \end{myitemize}

To get

Of course this is not even close to the normal itemize, as is not possible to page break nor do nested itemizes, there are also some problems with alignment of the circle and the label enumeration which can be overcomed with fine adjusments like yshift. Other fine tuning is possible using all TikZ wizardry, such as done with shorten < in the above example.

Finally, the vertical space flexibility is achieved with the \\ at the end of each line, which can be passed an optional argument, being that the vertical space between lines on that row, or the separation between all rows can be set using row sep.

The complete MWE

\documentclass{standalone}
\usepackage{tikz,etoolbox,amsmath}
\usetikzlibrary{matrix,backgrounds}
\newcounter{myitem}
\renewcommand*{\themyitem}{\Alph{myitem}.}
\newcommand{\myitem}{%
    \ifnumequal{\value{myitem}}{1}%
    {|[myitem label=M-0]| \pgfmatrixnextcell[\myitemizelabelsep] \themyitem\stepcounter{myitem} \pgfmatrixnextcell[\myitemizenumlabelsep]}%
    {|[myitem label=M-1]| \pgfmatrixnextcell \themyitem\stepcounter{myitem} \pgfmatrixnextcell}%
}
\newenvironment{myitemize}[1][]{%
\setcounter{myitem}{1}
\let\item\myitem
\begin{tikzpicture}[
    myitem label/.style={circle, fill= white, minimum size=.5em, name=##1},
    myitem label style/.style={myitem label/.append style={##1}},
    label sep/.store in=\myitemizelabelsep, label sep=.5em,
    numlabel sep/.store in=\myitemizenumlabelsep, numlabel sep=.2em,
    label background/.style={label background style/.style={##1}}, label background={},
    row sep=.75em,
    #1]
\matrix[matrix of nodes, nodes={inner sep=0pt}, column 1/.style={anchor=south}, column 3/.style={anchor=base west}]\bgroup%
}{%
\\\egroup;
\scoped[on background layer]{
    \path[line cap=round, label background style] (M-0.center) -- (M-1.center);};
\end{tikzpicture}
\undef{\item}
}
\begin{document}
    \begin{myitemize}[%
        myitem label style={fill=black,yshift=.2mm},
        label background={draw, gray, line width=1.2em, shorten <=-2mm}]
        \item $\dfrac{1}{2}$\\
        \item \draw[scale=0.5] (4,-1.5) node[shift={(-20:-.5)}, centered]{$\theta$} -| coordinate[pos=.5](rect) node[pos=.25, below]{4} node[pos=.75,left](tmp){3} ++(-4,3) -- cycle;
              \draw (rect) rectangle node[circle, fill=black, inner sep=0pt, minimum size=1.5pt, centered]{} ++(.2,.2);\\
        \item Something else\\
    \end{myitemize}
\end{document}

When coming to think of this now, perhaps a tabular is more suited...