Multicol and enumerate misalignment

Question

I want to place two enumerate environments side by side with multicol:

\usepackage{enumitem}

\begin{multicols}{2}
\begin{enumerate}[label=\Alph*.]
\item First
    \begin{enumerate}[label={\arabic*.}]
    \item \emph{Trial 1}
    \item \emph{Trial 2}
    \item \emph{Trial 3}
    \item \emph{Trial 4}
    \end{enumerate}
\columnbreak
\item Second
    \begin{enumerate}[label={\arabic*.}]
    \item \emph{Trial 5}
    \item \emph{Trial 6}
    \item \emph{Trial 7} 
    \end{enumerate}
\end{enumerate}
\end{multicols}

The first item has 1 more sub-item than the second, so the output is misaligned

A solution using an invisible placeholder would also be acceptable.

Answer 1

Here is an alternavite using two side-by-side top aligned minipages and the seriesand resume keys for the outer enumerate environment:

\documentclass{article}
\usepackage{enumitem}
\begin{document}
\begin{minipage}[t]{0.5\textwidth}
  \begin{enumerate}[label=\Alph*., series=outer]
  \item First
    \begin{enumerate}[label={\arabic*.}]
    \item \emph{Trial 1}
    \item \emph{Trial 2}
    \item \emph{Trial 3}
    \item \emph{Trial 4}
    \end{enumerate}
  \end{enumerate}
\end{minipage}%
\begin{minipage}[t]{0.5\textwidth}
  \begin{enumerate}[label=\Alph*., resume=outer]
  \item Second
    \begin{enumerate}[label={\arabic*.}]
    \item \emph{Trial 5}
    \item \emph{Trial 6}
    \item \emph{Trial 7} 
    \end{enumerate}
  \end{enumerate}
\end{minipage}
\end{document}

Answer 2

Adding a line break at the last item works as a placeholder.

\begin{multicols}{2} 
\begin{enumerate}[label=\Alph*.] 
\item First
    \begin{enumerate}[label={\arabic*.}]
    \item \emph{Trial 1}
    \item \emph{Trial 2}
    \item \emph{Trial 3}
    \item \emph{Trial 4}
    \end{enumerate} \columnbreak
\item Second
    \begin{enumerate}[label={\arabic*.}]
    \item \emph{Trial 5}
    \item \emph{Trial 6}
    \item \emph{Trial 7}  \\
    \end{enumerate}
\end{enumerate}
\end{multicols}