Htydjtk

Edit: Now I realize there is a issue with very long notes, specially because I am working with A5 paper.
Using Mica's solution:

Having the tablenotes flushleft however works just fine.

Two questions in one:

• How do I align the tablenotes to start at the left of the table and figure? (The flushleft option of threeparttable does affect the whole threeparttable and creates inconsistency)


• Why my code displays this difference in the tablenotes, when comparing figure and table?

documentclass{memoir}

usepackage{lmodern}            % Usa a fonte Latin Modern          

usepackage[T1]{fontenc}        % Selecao de codigos de fonte.

usepackage[utf8]{inputenc}     % Codificacao do documento (conv. auto. dos acentos)

usepackage[brazil]{babel}

usepackage[range-phrase={,a,}]{siunitx}

sisetup{

    group-digits=true,

    group-four-digits=true,

    group-separator={,},

    output-decimal-marker={,}

}

usepackage{caption}

captionsetup{

    justification=justified,

    %labelsep=quad,

    labelsep=endash, %% ABNT q manda

    position=above,

    skip=onelineskip,

    width=0.95linewidth,

}

setfloatadjustment{table}{centering}

setfloatadjustment{figure}{centering}

setfloatadjustment{threeparttable}{centering}

usepackage{tikz}

usepackage{pgfplots}

usepackage{threeparttable}





begin{document}        

begin{figure}

    captionof{figure}{Pressão}

    label{fig:pvapor2}

    begin{threeparttable}

        begin{tikzpicture}

        begin{axis}[grid=both,trim axis left, trim axis right,

        xlabel={Something else}, ylabel={Something},

        xmin= 1150,

        xmax=1550,

        ymin=-0.02

        ]

        addplot+[ultra thick] coordinates { 

            (1300-273,101325*4.278*10^-11)

            (1400-273,101325*8.133*10^-10)

            (1500-273,101325*1.040*10^-8)

            (1600-273,101325*9.636*10^-8)

            (1687-273,101325*5.377*10^-7)

            (1700-273,101325*6.662*10^-7)

            (1800-273,101325*3.117*10^-6)

            (1900-273,101325*1.238*10^-5)

        };

        end{axis}

        end{tikzpicture}

        begin{tablenotes}

            item Fonte: Autor.

        end{tablenotes}

    end{threeparttable}

end{figure}



begin{table}

    captionof{table}{Planejamento}

    label{tab:planejamentoexperimental}

    begin{threeparttable}[t]

        begin{tabular}{@{}SSSS @{}}

            toprule

            text{Ordem} & text{Ensaio} & text{Fator A} & text{Fator B} \

            midrule

            12 & 1 & 0 & 0\

            5 & 2 & -1.41421 & 0\

            2 & 3 & 1 & -1\

            11 & 4 & 0 & 0\

            13 & 5 & 0 & 0\

            10 & 6 & 0 & 0\

            8 & 7 & 0 & 1.41421\

            1 & 8 & -1 & -1\

            9 & 9 & 0 & 0\

            7 & 10 & 0 & -1.41421\

            3 & 11 & -1 & 1\

            4 & 12 & 1 & 1\

            6 & 13 & 1.414214 & 0\

            bottomrule

        end{tabular}

        begin{tablenotes}

            item Fonte: Autor.

        end{tablenotes}

    end{threeparttable}

end{table}

end{document}

In the following example, I have used the flushleft option to the individual tablenotes environments. I have also embedded the tikzpicture in a tabular environment to overcome the alignment issue there.

documentclass{memoir}

usepackage{lmodern}            % Usa a fonte Latin Modern          

usepackage[T1]{fontenc}        % Selecao de codigos de fonte.

usepackage[utf8]{inputenc}     % Codificacao do documento (conv. auto. dos acentos)

usepackage[brazil]{babel}

usepackage[range-phrase={,a,}]{siunitx}

sisetup{

    group-digits=true,

    group-four-digits=true,

    group-separator={,},

    output-decimal-marker={,}

}

usepackage{caption}

captionsetup{

    justification=justified,

    %labelsep=quad,

    labelsep=endash, %% ABNT q manda

    position=above,

    skip=onelineskip,

    width=0.95linewidth,

}

setfloatadjustment{table}{centering}

setfloatadjustment{figure}{centering}

setfloatadjustment{threeparttable}{centering}

usepackage{tikz}

usepackage{pgfplots}

usepackage{threeparttable}





begin{document}        

begin{figure}

    caption{Pressão}

    label{fig:pvapor2}

    begin{threeparttable}

    begin{tabular}{@{}c@{}}

        begin{tikzpicture}

        begin{axis}[grid=both,trim axis left, trim axis right,

        xlabel={Something else}, ylabel={Something},

        xmin= 1150,

        xmax=1550,

        ymin=-0.02

        ]

        addplot+[ultra thick] coordinates { 

            (1300-273,101325*4.278*10^-11)

            (1400-273,101325*8.133*10^-10)

            (1500-273,101325*1.040*10^-8)

            (1600-273,101325*9.636*10^-8)

            (1687-273,101325*5.377*10^-7)

            (1700-273,101325*6.662*10^-7)

            (1800-273,101325*3.117*10^-6)

            (1900-273,101325*1.238*10^-5)

        };

        end{axis}

        end{tikzpicture}

        end{tabular}

        begin{tablenotes}[flushleft]

            item Fonte: Autor.

        end{tablenotes}

    end{threeparttable}

end{figure}



begin{table}

    caption{Planejamento}

    label{tab:planejamentoexperimental}

    begin{threeparttable}[t]

        begin{tabular}{@{}SSSS @{}}

            toprule

            text{Ordem} & text{Ensaio} & text{Fator A} & text{Fator B} \

            midrule

            12 & 1 & 0 & 0\

            5 & 2 & -1.41421 & 0\

            2 & 3 & 1 & -1\

            11 & 4 & 0 & 0\

            13 & 5 & 0 & 0\

            10 & 6 & 0 & 0\

            8 & 7 & 0 & 1.41421\

            1 & 8 & -1 & -1\

            9 & 9 & 0 & 0\

            7 & 10 & 0 & -1.41421\

            3 & 11 & -1 & 1\

            4 & 12 & 1 & 1\

            6 & 13 & 1.414214 & 0\

            bottomrule

        end{tabular}

        begin{tablenotes}[flushleft]

            item Fonte: Autor.

        end{tablenotes}

    end{threeparttable}

end{table}

end{document}

Given that you're not using any tnote directives, employing the threeparttable machinery and a tablenotes environment seems inappropriate or, at the least, like massive overkill. The simplest solution for your formatting objective would appear to consist of place the "Fonte" ("source", right?) line into the body of the tabular environment. In the code below, that's done by writing

multicolumn{4}{@{}l}{footnotesize Fonte: Autor.}

While you're making ajdustments, you should be a bit more deliberate in the way you use the S column type, especially in view of the fact that the SSSS one-size-fits-all approach is ill advised.

The same argument holds for the treatment of the material in the figure environment: There's no need for the threeparttable environment machinery. Just place the tikzpicture environment in a single-column tabular environment, with column type @{}l@{}, and let the second row consist of

footnotesize Fonte: Autor. % second "row"

documentclass{memoir}

usepackage{lmodern}     % Usa a fonte Latin Modern          

usepackage[T1]{fontenc} % Selecao de codigos de fonte.

usepackage[utf8]{inputenc} 

usepackage[brazil]{babel}

usepackage{siunitx}

sisetup{range-phrase={,a,},

         group-digits=true,

         group-four-digits=true,

         group-separator={,},

         output-decimal-marker={,}

         }

usepackage{caption}

captionsetup{justification=justified,

              %labelsep=quad,

              labelsep=endash, %% ABNT q manda

              position=above,

              skip=1ex,

              %width=0.95linewidth,

              }

setfloatadjustment{table}{centering}



usepackage{tikz}

usepackage{pgfplots}



begin{document}        

setcounter{chapter}{2} % just for this example



begin{table}

    caption{Planejamento}

    label{tab:planejamentoexperimental}

    begin{tabular}{@{} *{2}{S[table-format=2.0]}

                        *{2}{S[table-format=-1.5]} @{}}

    toprule

    {Ordem} & {Ensaio} & {Fator A} & {Fator B} \

    midrule

    12 & 1 & 0 & 0\

    5 & 2 & -1.41421 & 0\

    2 & 3 & 1 & -1\

    11 & 4 & 0 & 0\

    13 & 5 & 0 & 0\

    10 & 6 & 0 & 0\

    8 & 7 & 0 & 1.41421\

    1 & 8 & -1 & -1\

    9 & 9 & 0 & 0\

    7 & 10 & 0 & -1.41421\

    3 & 11 & -1 & 1\

    4 & 12 & 1 & 1\

    6 & 13 & 1.414214 & 0\

    bottomrule

    addlinespace

    multicolumn{4}{@{}l}{footnotesize Fonte: Autor.}

    end{tabular}

end{table}



begin{figure}[h!]

    centering

    caption{Pressão}

    label{fig:pvapor2}

    begin{tabular}{@{}l@{}}

    begin{tikzpicture}

    begin{axis}[grid=both,trim axis left, trim axis right,

        xlabel={Something else}, ylabel={Something},

        xmin= 1150,

        xmax=1550,

        ymin=-0.02

        ]

        addplot+[ultra thick] coordinates { 

            (1300-273,101325*4.278*10^-11)

            (1400-273,101325*8.133*10^-10)

            (1500-273,101325*1.040*10^-8)

            (1600-273,101325*9.636*10^-8)

            (1687-273,101325*5.377*10^-7)

            (1700-273,101325*6.662*10^-7)

            (1800-273,101325*3.117*10^-6)

            (1900-273,101325*1.238*10^-5)

        };

    end{axis}

    end{tikzpicture}\ % end of first "row"

    footnotesize Fonte: Autor. % second "row"

    end{tabular}

end{figure}

end{document}