Based on UlrikeFischer's explanation, I tried the following just to experiment. In case it helps anyone, posting it here. And do not forget to compile twice if using hyperref for pdfbookmarks.
\documentclass{article}
\usepackage{hyperref}
\begin{document}
\section{Section Bookmark}
\newpage
\pdfbookmark[0]{Text A}{targetA} A
\newpage
\pdfbookmark[1]{Text B}{targetB} B
\newpage
\pdfbookmark[2]{Text C}{targetC} C
\newpage
\pdfbookmark[2]{Text D}{targetD} D
\newpage
\pdfbookmark[4]{Text E}{targetE} E Skipped Level
\newpage
\pdfbookmark[3]{Text F}{targetF} F
\newpage
\pdfbookmark[1]{Text G}{targetG} G
\newpage
\pdfbookmark[2]{Text H}{targetH} H
\newpage
\pdfbookmark[0]{Text I}{targetI} I
\end{document}

And here's how bookmark package works:
\documentclass{article}
\usepackage{bookmark}
\begin{document}
\section{Section Bookmark}
\newpage
\hypertarget{targetA}{}
\bookmark[level=0,dest=targetA]{Text A} A
\newpage
\hypertarget{targetB}{}
\bookmark[level=1,dest=targetB]{Text B} B
\newpage
\hypertarget{targetC}{}
\bookmark[level=2,dest=targetC]{Text C} C
\newpage
\hypertarget{targetD}{}
\bookmark[level=2,dest=targetD]{Text D} D
\newpage
\hypertarget{targetE}{}
\bookmark[level=4,dest=targetE]{Text E} E Skipped Level
\newpage
\hypertarget{targetF}{}
\bookmark[level=3,dest=targetF]{Text F} F
\newpage
\hypertarget{targetG}{}
\bookmark[level=1,dest=targetG]{Text G} G
\newpage
\hypertarget{targetH}{}
\bookmark[level=2,dest=targetH]{Text H} H
\newpage
\hypertarget{targetI}{}
\bookmark[level=0,dest=targetI]{Text I} I
\end{document}

\newcommand\pdfbookmark[3][]{}means 3 args, 1 optional arg, 2 mandatory args. – Peter Grill May 19 '23 at 04:51