Enumerated list in subsubsection style

Question

How can I define a list environment using a package like enumitem such that it reproduces the same output as the following code but with the syntax of an enumerated list:

\documentclass[a4paper,12pt]{article}

\usepackage{lipsum}

\begin{document}

\subsubsection*{Item 1}
\lipsum[1]

\subsubsection*{Item 2}
\lipsum[2]

\subsubsection*{Item 3}
\lipsum[3]

%% The following syntax should produce the same as above.

% \begin{mylist}
%   \item 
%     \lipsum[1]
%   \item 
%     \lipsum[2]
%   \item 
%     \lipsum[3]
% \end{mylist}

\end{document}

Desired output:

Answer 1

Here is a possibility

\documentclass[a4paper,12pt]{article}
\usepackage{lipsum}
\usepackage{calc}
\usepackage[inline]{enumitem}
\newlist{mylist}{enumerate}{1}
\setlist[mylist]{
    label=\bfseries Item \arabic*,
    labelwidth=\widthof{last-item},
    leftmargin=!,
    align=left,
    itemindent=1.8cm,
    itemsep=10pt
}

\newcommand{\myitem}{\item~\\[6pt]}
\begin{document}
\subsubsection*{Item 1}
\lipsum[1]

\subsubsection*{Item 2}
\lipsum[2]

\subsubsection*{Item 3}
\lipsum[3]

%% The following syntax should produce the same as above.


 \begin{mylist}
   \myitem
     \lipsum[1]
   \myitem 
     \lipsum[2]
   \myitem 
     \lipsum[3]
 \end{mylist}

\end{document}

I had to redefine \item too so to send the item text to a new line.

labelwidth=\widthof{last-item},
leftmargin=!,
align=left,

are for setting the label next to the margin. To automatically calculate the largest label width the package calc is needed.

itemindent=1.8cm,

is for removing the indent of the item text (this is the only value I wasn't able to compute automatically but should be fixed, so not a big deal)

itemsep=10pt

sets the vertical space between items

\newcommand{\myitem}{\item~\\[6pt]}

sends the item text to a newline with a vertical space of 6pt from the label.

Answer 2

A very simple code, which lets you use the usual \item command:

\documentclass[a4paper,12pt]{article}
\usepackage{lipsum}
\usepackage{enumitem}
\newlist{mylist}{enumerate}{1}

\setlist[mylist]{label=\raisebox{0pt}[4ex][3ex]{\makebox[\textwidth][l]{\bfseries Item \arabic*}}, wide = 0pt}

\begin{document}

 \begin{mylist}
   \item
     \lipsum[1]
   \item
     \lipsum[2]
   \item
     \lipsum[3]
 \end{mylist}

\end{document}