Equal spacing only between some columns of a table

booktabstablestabularxthreeparttable

I am trying to make this table look nicer, I've tried the >{\hsize=.85\hsize} trick, but can't get it last part to be short. I am almost sure there is more elegant solution. Basically I need the last three columns to be equally spaced and almost-same-size.

(arbitrary margin just to match my institution requirements without loading custom packages)
MWE:

\documentclass[,a4paper]{memoir}
\usepackage[adobe-utopia]{mathdesign}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{tabularx}
\usepackage{threeparttable}
\usepackage{booktabs}
\usepackage[margin=3.8cm]{geometry}
%***********************Document*******************
\begin{document}
    \begin{threeparttable}{\small 
            \linespread{1.3}\selectfont{}
            \begin{tabularx}{\textwidth}{@{}XXXX@{}}\toprule
                Factor & Low & Medium & High\\
                \midrule
                Physiochemical & & &\\ 
                \hspace{1em}Smothing abc.\ & Molecular flow & Molecular flow & Continuum flow \\ 
                \hspace{1em}Sticking coef.\ & Reversible adsorption & Adsorption & High eff.\ adsorption\\ 
                \hspace{1em}Available mol.\ & Insufficient coverage & Surface saturation & {Precursor waste \tnote{$\dagger$}}\\
                \addlinespace[1ex] %\hdashline
                \midrule
                Processing &  &  & \\ 
                %\cmidrule(){1-1}
                \hspace{1em}{Temperature} & {Condensation} & {Adsorption} & {Desorption \tnote{$\star$}}\\ 
                \hspace{1em}Pressure & Poor precursor carrier & Balanced & Lower interdiffusion\\ 
                \hspace{1em}Exposure time & Insufficient coverage & Complete coverage & Longer cycle\\
                
                \bottomrule
        \end{tabularx}}
        
        \begin{tablenotes}
            \item[$\dagger$] Another thing.
            \item[$\star$] Something.
            \item Source: BBQ.
        \end{tablenotes}
    \end{threeparttable}
\end{document}

Desired result like this:

desired table with annonations

I have read through a lot of questions, specially this and this other one. Most questions seem to related either to, multicolumn, long table, or number-content tables, which is not my case.

Best Answer

Based on the annotated screenshot you posted, it looks like you want equal amounts of whitespace between the columns and no whitespace to the right of the final column. A tabular* environment lets you achieve these formatting objectives.

enter image description here

\documentclass[a4paper]{memoir}
\usepackage[adobe-utopia]{mathdesign}
%%\usepackage[utf8]{inputenc} % that's the default nowadays
\usepackage[T1]{fontenc}
\usepackage{array}
\newcommand\mc[1]{\multicolumn{1}{@{}l}{#1}} % handy shortcut macro

\usepackage[flushleft]{threeparttable}
\usepackage{booktabs}
\usepackage[margin=3.8cm]{geometry}

\begin{document}

\noindent
\begin{threeparttable} 
%% \small % not needed
\setlength\tabcolsep{0pt} % default: 6pt
\linespread{1.15} % "\linespread{1.3}" seems excessive
\begin{tabular*}{\textwidth}{@{\extracolsep{\fill}} >{\quad}l lll }
\toprule
     \mc{Factor} & Low & Medium & High\\
     \midrule
     \mc{Physiochemical} \\ 
     Smoothing abc.\ & Molecular flow & Molecular flow & Continuum flow \\ 
     Sticking coeff.\ & Reversible adsorption & Adsorption & High eff.\ adsorption\\ 
     Available mol.\ & Insufficient coverage & Surface saturation & Precursor waste\tnote{$\dagger$} \\
     \midrule
     \mc{Processing} \\ 
     Temperature & Condensation & Adsorption & Desorption\tnote{$\star$}\\ 
     Pressure & Poor precursor carrier & Balanced & Lower interdiffusion\\ 
     Exposure time & Insufficient coverage & Complete coverage & Longer cycle\\
\bottomrule
\end{tabular*}
      
\smallskip  
\footnotesize
\begin{tablenotes}
   \item[$\dagger$] Another thing.
   \item[$\star$] Something.
   \item[\phantom{$\dagger$}] Source: BBQ.
\end{tablenotes}
\end{threeparttable}

\end{document}
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