documentclass[listof=totoc]{scrreprt}

usepackage{bookmark}
bookmarksetup{
    open,
    addtohook={%
        ifnumbookmarkget{level}=0 %
        bookmarksetup{bold}%
        fi
    },
}


usepackage{graphicx}
usepackage{lipsum}
usepackage{mwe}

begin{document}
pdfbookmark[0]{Content}{toc}
tableofcontents
bookmarksetupnext{bold=false}
listoffigures
newpage

chapter{Chapter 1}
lipsum[1]
begin{figure}[h]
includegraphics[width=textwidth]{example-image-a}
caption{I am a figurelabel{fig:one}}
end{figure}
section{Section 1}
lipsum[1]
begin{figure}[h]
includegraphics[width=textwidth]{example-image-a}
caption{I am a figurelabel{fig:one}}
end{figure}

bookmarksetupnext{bold=false}
appendix
addtocontents{toc}{protectcontentsline {chapter}{Appendix}{}{}}
chapter{App 1}
lipsum[1]
end{document}

documentclass[listof=totoc]{scrreprt}

usepackage{bookmark}
bookmarksetup{
    open,
    addtohook={%
        ifnumbookmarkget{level}=0 %
        bookmarksetup{bold}%
        fi
    },
}

usepackage{graphicx}
usepackage{lipsum}
usepackage{mwe}

begin{document}
pdfbookmark[0]{Content}{toc}
tableofcontents
bookmarksetupnext{addtohook=bookmarksetup{bold=false}}
listoffigures
newpage

chapter{Chapter 1}
lipsum[1]
begin{figure}[h]
includegraphics[width=textwidth]{example-image-a}
caption{I am a figurelabel{fig:one}}
end{figure}
section{Section 1}
lipsum[1]
begin{figure}[h]
includegraphics[width=textwidth]{example-image-a}
caption{I am a figurelabel{fig:two}}
end{figure}

bookmarksetupnext{addtohook=bookmarksetup{bold=false}}
appendix
addtocontents{toc}{protectcontentsline {chapter}{Appendix}{}{}}
chapter{App 1}
lipsum[1]
end{document}