how to put footnote in the table?

Question

I want to put footnote for AAAAAAAAA

\documentclass[review]{elsarticle}
\usepackage{geometry}
\usepackage{epsfig}
\usepackage{latexsym}
\usepackage[font={normalsize}]{caption}
\usepackage[para,flushleft]{threeparttable}
\renewcommand{\TPTtagStyle}{\textit}
\usepackage{booktabs}
%\usepackage{nicematrix}
\usepackage{amsmath}
\usepackage{fullpage}
\usepackage{setspace}
\usepackage{mathtools}
\usepackage{fancyhdr}
\usepackage{sectsty}
\usepackage{siunitx}
\usepackage{tabularx}
\usepackage{float}
\usepackage{indentfirst}
\usepackage{changepage}
\usepackage{adjustbox}
\usepackage{tabularx}
\usepackage{rotating}
\usepackage{makecell}
\usepackage{subcaption}
\usepackage{rotating}
%\usepackage{subfigure}
\linespread{1}
\usepackage[hidelinks]{hyperref}
% packages for tables
\usepackage{multirow}
\usepackage[table,xcdraw]{xcolor}
\usepackage{graphicx}
\usepackage{graphics}
\usepackage{caption}
\usepackage{color,soul}
\usepackage{fullpage} 
\usepackage[skip=1ex, 
            font=small, labelfont=bf]{caption}
% packages for tables
\usepackage[table,xcdraw]{xcolor}
\usepackage{multirow, tabularx}
\usepackage{tabularray}
\UseTblrLibrary{booktabs, siunitx, varwidth}
\usepackage{tablefootnote}
\usepackage{enumitem}
\usepackage{lineno,hyperref}
\modulolinenumbers[5]
\begin{document}
\renewcommand{\arraystretch}{2}
\begin{table}[H]
\centering
\caption{Grid search leaderboard}
\begin{tabular}{ccccccc}
\hline
 Test No.& type&SeASDues & $R^2$ & PrAcessing& ML moADls& MeSDFaASFdel \ \hline
1 & Stacked  & 12 & 0.96 & PCA & PolyFASres, EADR, DTR, GSDFR & LassoLarsCV\
2 & Stacked &  14 & 0ASD3& ZeroSDnt, MinMaSDFDaler& DT, ETR, RiSFe&XGB\
3 & Stacked &  17 & 0.96 &  ZeroCASDunt,RobASDScaler&RiSDgeCV&XBG\
\textbf{4} & \textbf{Stacked} & \textbf{18}& \textbf{0SDF8}& \textbf{MinMADScaler, RobustScaler}& \textbf{GBR, PolyFeADres, LassoLarsCV} & \textbf{RSFgeCV} \
\textbf{5} &  \textbf{Stacked} & \ASDA& \ASDASD9 & \textbf{TTT} & \textbf{GBR, PSDFADes, SGD, DTR} & \textbf{LassoLarsCV}\
6 & Stacked &20 & 0SDF5 &-& RF,  AAAAAAAAAA    , PolyFeatSDFres  &LassoLarsCV\
7 & Stacked & 75 & 0.SD6 & -&F_regression, XGB & XGB\
 8& Stacked & 100 & 0.95 &ZeroCount, RobustScaler, MaxAbsScaler & XGB, Ridge & GBR\
\textbf{9} &  \textbf{ANN} & \textbf{12}&\textbf{0.80} &\textbf{MinMaxScaler} &\textbf{[13,32,32,1]}  &\textbf{-}\
10 &ANN &16  & 0.53 & MinMaxScaler  & [13,512,128,1]& - \
 11& ANN & 22 & 0.71 &MinMaxScaler& [13,64,512,1] &-\
 12& ANN & 100 & 0.77 & MinMaxScaler & [13,128,1024,16,1] &-\ \hline
\end{tabular}
\end{table}
\end{document}

Answer 1

To long for the comment ...

• Your document example unfortunately doesn't work. It also afzer your edits still use some undefined commands.
• It not contain any footnote. Please add it where you like to have \footnotemark
• Do you really need all those packages? Some of them are already loaded by other packages, some are loaded twice ... Cleanup your preamble!
• Package hyperref should be loaded last.

For starting point you may for table xtabularx use and define forth and fifth column as L type, for which in preamble define \newcolumntype{L}{>{\raggedright\arraybackslash}X}:

\begin{table}[ht]
\centering
\caption{Grid search leaderboard}
\setlength\tabcolsep{4pt}
\small
\begin{tabularx}{\linewidth}{@{} cccl LL l @{}}
\hline
\makecell{Test\\ No.} & type & \makecell{SeAS\\Dues} & $R^2$ & PrAcessing& ML moADls& \makecell{MeSD-\\ FaASFdel} \\ \hline

By this changes, your table will fit in text block:

For inserting footnotes, Please first edit your question again with considering aforementioned. Then We will be able simple add desired footnote.

Answer 2

Since your code loads the threeparttable package, you might as well make use of it to generate the desired footnote. Please see the code below for an example of how to employ \tnote directives and the tablenotes environment.

To make the table fit inside the width of the text block, I suggest you employ a tabularx environment and employ the X column type for columns 5 and 6.

\documentclass[review]{elsarticle}
\usepackage{geometry}
%%\usepackage{epsfig}
%%\usepackage{latexsym} % latexsym was superseded by amssymb in 1994
\usepackage{amssymb}
%%\usepackage[font=normalsize]{caption}
\usepackage[para,flushleft]{threeparttable}
\renewcommand{\TPTtagStyle}{\textit}
\usepackage{booktabs}
%\usepackage{nicematrix}
\usepackage{amsmath}
\usepackage{fullpage}
\usepackage{setspace}
\usepackage{mathtools}
\usepackage{fancyhdr}
\usepackage{sectsty}
\usepackage{siunitx}
\usepackage{tabularx}
\usepackage{float}
\usepackage{indentfirst}
\usepackage{changepage}
\usepackage{adjustbox}
%%\usepackage{tabularx}
\usepackage{rotating}
\usepackage{makecell}
\usepackage{caption,subcaption}
\captionsetup{skip=1ex, font=small, labelfont=bf} % are you sure about "font=small"?
\usepackage{rotating}
%\usepackage{subfigure}
\linespread{1}
\usepackage[hidelinks]{hyperref}
% packages for tables
\usepackage{multirow}
\usepackage[table,xcdraw]{xcolor}
\usepackage{graphicx}
%%%\usepackage{graphics}
%%%\usepackage{caption}
\usepackage{color,soul}
%%\usepackage{fullpage}
% packages for tables
\usepackage[table,xcdraw]{xcolor}
\usepackage{multirow} %%%, tabularx}
\usepackage{tabularray}
\UseTblrLibrary{booktabs, siunitx, varwidth}
%%\usepackage{tablefootnote}
\usepackage{enumitem}
\usepackage{lineno}  %%,hyperref}
\modulolinenumbers[5]
%% new code:
\usepackage{lipsum}
\newcolumntype{L}{>{\raggedright\arraybackslash}X}
\begin{document}
%\renewcommand{\arraystretch}{2} % seems excessive
\begin{table}[ht]
%%\centering % not needed
\begin{threeparttable}
\caption{Grid search leaderboard}
\label{GridASDASDh}
% Allow automatic line breaks in columns 5 and 6:
\begin{tabularx}{\textwidth}{@{} l ccc LL l @{}}
\toprule %\hline
 Test No.& type & SeASDues & $R^2$ & PrAcessing & ML moADls & MeSDFaASFdel \
\midrule %\hline
1 & Stacked & 12 & 0.96 & PCA & PolyFASres, EADR, DTR, GSDFR & LassoLarsCV\
\addlinespace
2 & Stacked & 14 & 0ASD3& ZeroSDnt, MinMaSDFDaler& DT, ETR, RiSFe&XGB\
\addlinespace
3 & Stacked & 17 & 0.96 &  ZeroCASDunt, RobASDScaler & RiSDgeCV & XBG\
\addlinespace
\textbf{4} & \textbf{Stacked} & \textbf{18} & \textbf{0SDF8} & \textbf{MinMADScaler, RobustScaler}& \textbf{GBR, PolyFeADres, LassoLarsCV} & \textbf{RSFgeCV} \
\addlinespace
\textbf{5} & \textbf{Stacked} & ASDA & ASDASD9 & \textbf{TTT} & \textbf{GBR, PSDFADes, SGD, DTR} & \textbf{LassoLarsCV}\
\addlinespace
6 & Stacked & 20 & 0SDF5 & -- & RF, AAAAAAAAAA,\tnote{a} PolyFeatSDFres  &LassoLarsCV\
\addlinespace
7 & Stacked & 75 & 0.SD6 & -- & F_regression, XGB & XGB\
\addlinespace
8 & Stacked & 100& 0.95 & ZeroCount, RobustScaler, MaxAbsScaler & XGB, Ridge & GBR\
\addlinespace
\textbf{9} & \textbf{ANN} & \textbf{12} & \textbf{0.80}     & \textbf{MinMaxScaler} & \textbf{[13,32,32,1]} & \textbf{--}\
\addlinespace
10& ANN     & 16 & 0.53 & MinMaxScaler & [13,512,128,1]     & -- \
\addlinespace
11& ANN     & 22 & 0.71 & MinMaxScaler & [13,64,512,1]      & -- \
\addlinespace
12& ANN     & 100& 0.77 & MinMaxScaler & [13,128,1024,16,1] & -- \
\bottomrule %\hline
\end{tabularx}
\smallskip\footnotesize
\begin{tablenotes}
\item[a] Some footnote text.
\end{tablenotes}
\end{threeparttable}
\end{table}
\lipsum[1-5] % filler text
\end{document}