Creating a list with reduced spacing, no bullets and level 1 in bold

Question

Trying to make a small topic list in the left side of a two column page using flowfram. I have tried making the list using itemize, but have been unable to make the spacing sufficiently small between Caption and sub Caption.

This is the closest I have gotten to the visuals i want. What I want to do is in the image in the bottom.

\documentclass[a4paper,12pt]{memoir} % Font and paper size
\usepackage{flowfram} % Required for the multi-column layout

% Define the left frame (sidebar)
\newflowframe{0.28\textwidth}{\textheight}{0pt}{0pt}[left]
\newlength{\LeftMainSep}
\setlength{\LeftMainSep}{0.28\textwidth}
\addtolength{\LeftMainSep}{1\columnsep}
 
% Define the right frame (main body)
\addtolength{\LeftMainSep}{1.5pt}
\addtolength{\LeftMainSep}{1\columnsep}
\newflowframe{0.65\textwidth}{\textheight}{\LeftMainSep}{0pt}[main01]

\pagestyle{empty} % Disable all page numbering

\setlength{\parindent}{0pt} % Stop paragraph indentation


\begin{document}
    {\small\textbf{Here is a caption 1}}\\
    {\tiny Caption 1 subtext}\\

    {\small\textbf{Here is a caption 2}}\\
    {\tiny Caption 2 subtext}\\
    
    {\small \textbf{Here is caption 3}}\\
    {\tiny Caption 3 subtext}\\
        
    {\small \textbf{Here is caption 4}}\\
    {\tiny Caption 4 subtext}\\
\end{document}  

Answer 1

For the baseline distance always the \baselineskip at the end of the paragraph is the valid one. Because of the grouping with {\small…} and {\tiny…} the \baselineskip of \normalsize is relevant for all lines of your code. You can, e.g., use:

\documentclass[a4paper,12pt]{memoir} % Font and paper size
\usepackage{flowfram} % Required for the multi-column layout

% Define the left frame (sidebar)
\newflowframe{0.28\textwidth}{\textheight}{0pt}{0pt}[left]
\newlength{\LeftMainSep}
\setlength{\LeftMainSep}{0.28\textwidth}
\addtolength{\LeftMainSep}{1\columnsep}
 
% Define the right frame (main body)
\addtolength{\LeftMainSep}{1.5pt}
\addtolength{\LeftMainSep}{1\columnsep}
\newflowframe{0.65\textwidth}{\textheight}{\LeftMainSep}{0pt}[main01]

\pagestyle{empty} % Disable all page numbering

\setlength{\parindent}{0pt} % Stop paragraph indentation


\begin{document}
\raggedright
    \small\textbf{Here is a caption 1}\\
    \tiny Caption 1 subtext\par\normalsize\vspace{\baselineskip}

    \small\textbf{Here is a caption 2}\\
    \tiny Caption 2 subtext\par\normalsize\vspace{\baselineskip}
    
    \small \textbf{Here is caption 3}\\
    \tiny Caption 3 subtext\par\normalsize\vspace{\baselineskip}
        
    \small \textbf{Here is caption 4}\\
    \tiny Caption 4 subtext\par\normalsize
\end{document}