documentclass{article}
usepackage[utf8]{inputenc}
usepackage[english]{babel}
usepackage[T1]{fontenc}

begin{document}

{scriptsizebegin{itemize}
    item Item 1
    begin{itemize}
        item Item 1a
        item Item 1b
    end{itemize}
    item Item 2
    begin{itemize}
        item Item 2a
        item Item 2b
    end{itemize}
end{itemize}}

end{document}

documentclass{article}
usepackage[utf8]{inputenc}
usepackage[english]{babel}
usepackage[T1]{fontenc}

usepackage{tasks}

begin{document}

{scriptsizebegin{tasks}[style=itemize](2)
    task Item 1
    {begin{tasks}[item-indent=2pt](1)
        task[textendash] Item 1a
        task[textendash] Item 1b
    end{tasks}}
    task Item 2
    {begin{tasks}[item-indent=2pt](2)
        task[textendash] Item 2a
        task[textendash] Item 2b
    end{tasks}}
end{tasks}}

end{document}