Error Adding Rows in columns of a table

Question

I got a good answer for porting the standard table into a springer journal from answer here Latex Table Missing Border Lines using following code

\usepackage{xcolor}
\usepackage{tabularray}
\UseTblrLibrary{siunitx}
\begin{document}
    \begin{table}[ht]
    \caption{Result}
\sisetup{table-format=2.1,
         detect-weight, % <--
         }
\begin{tblr}{hlines, vlines,
             colspec = {X[c] X[1.2,c] X[1.8,c] X[c, si]},
             cell{even}{2} = {r=2}{},
             cell{odd[3]}{Z} = {font=\bfseries},
             row{1} = {guard}
             } 
Users Set Size (USS)
    &   Range of Users Individual
        &   Index of scalar array for mapping
            &   Transfer Failure        \
\SetCell[r=6]{c}    6
    & 6 & 10& 23                        \
    &   & 4 & 18.3                      \
    & 7 & 0 & 13.3                      \
    &   & 4 & 33.3                      \
    & 7 & 1 & 17                        \
    &   & 2 & 66.6                      \
\end{tblr}
   \end{table}
\end{document}

(image attached for above latex) but I need to add a row in each cell of columns 3 and 4. For example a row below 4 & 18.3, a row below 4 & 33.3 and a row below 2 & 66.6. so I am unable to understand where I need to modify I changed \SetCell[r=6]{c} to \SetCell[r=9]{c} but got strange output and error. Can anyone tell what I need to modify in this latex code

Answer 1

As complement to @Clara answer (+1) ...

• In my code, which you use in your question, the table preamble has the following meaning

\begin{tblr}{hlines, vlines,
     colspec = {X[c] X[1.2,c] X[1.8,c] X[c, si]}, % determine column types
     cell{even}{2} = {r=2}{}, % determine where multi row cells, which span 
                              % two successive rows start: at each even row 
                              % after second row
   cell{odd[3]}{Z} = {font=\bfseries}, % determine in which rows numbers in 
                              % the last columns are in the boldface shape
             row{1} = {guard} % protect text in the `S` columns in the first 
                              % row, that not interfere in S column formating
             }

• You not provide information, what are in those additional rows and if some numbers are in boldface.
• Assuming, that expecting result is similar to the following

than you need to make the following changes in code shown ion question:

\begin{tblr}{hlines, vlines,
     colspec = {X[c] X[1.2,c] X[1.8,c] X[c, si]},
     cell{2,5,8}{2} = {r=3}{},           % determine multi row cells in the second column
                                         % which span three successive adjacent rows
     cell{4,7,10}{Z} = {font=\bfseries}, % determine which cells in the last column are in boldface
     row{1} = {guard}
             }

• For more details, about used code, you should read tabularray packages documentation or ask (in comments), what in provided suggestions is not clear to you.
• For sake of completeness, the complete MWE, which generate above showed table, is:

\documentclass{sn-jnl}
\usepackage{xcolor}
\usepackage{tabularray}
\UseTblrLibrary{siunitx}
\begin{document}
    \begin{table}[ht]
    \caption{Result}
\sisetup{table-format=2.1,
         detect-weight, % <--
         }
\begin{tblr}{hlines, vlines,
     colspec = {X[c] X[1.2,c] X[1.8,c] X[c, si]},
     cell{2,5,8}{2} = {r=3}{},           % determine multi row cells in the second column
                                         % which span three successive adjacent rows
     cell{4,7,10}{Z} = {font=\bfseries}, % determine which cells in the last column are in boldface
     row{1} = {guard}
             }
Users Set Size (USS)
    &   Range of Users Individual
        &   Index of scalar array for mapping
            &   Transfer Failure        \
\SetCell[r=9]{c}    9    % multirow cell in the first column, spanning 9 rows
    & 6 & 10& 23                        \
    &   & 7 & 20                        \
    &   & 4 & 18.3                      \
    & 7 & 0 & 13.3                      \
    &   & 0 & 13.3                      \
    &   & 4 & 33.3                      \
    & 7 & 1 & 17                        \
    &   & 3 & 11                        \
    &   & 2 & 66.6                      \
\end{tblr}
   \end{table}
\end{document}

Answer 2

I'm not sure if this is what you're looking for. I suggest separating the style and content completely instead of mixing them together.

\documentclass{article}
\usepackage{tabularray}
\UseTblrLibrary{siunitx}
\begin{document}
\begin{table}
\caption{Result}
\begin{tblr}
{
colspec        = {X[c,m]X[1.2,c,m]X[1.8,c,m]X[c,m,si={table-format=2.1,detect-weight}]},
cell{2}{1}     = {r=9}{},
cell{2,5,8}{2} = {r=3}{},
cell{3,6,9}{Z} = {font=\bfseries},
row{1}         = {guard},
hlines,vlines,
}
Users Set Size (USS) & Range of Users Individual & Index of scalar array for mapping & Transfer Failure \\
6                    & 6                         & 10                                & 23               \\
                     &                           & 4                                 & 18.3             \\
                     &                           & 4                                 & 18.3             \\
                     & 7                         & 0                                 & 13.3             \\
                     &                           & 4                                 & 33.3             \\
                     &                           & 4                                 & 33.3             \\
                     & 7                         & 1                                 & 17               \\
                     &                           & 2                                 & 66.6             \\
                     &                           & 2                                 & 66.6             \\
\end{tblr}
\end{table}
\end{document}