Command \fillwithdottedlines (taken from exam documentclass) does not work in a table (Tabularray). Why? Can be fixed?

I am not completely sure what is really going wrong here (and therefore this is only a partial answer), but at least one of the problems stems from the definition of \fillwithdottedlines which requires that a space follows the argument (because the space delimits the argument). You can check this by writing into one of the cells in the left column \fillwithdottedlines{5cm} {}, which at least results in no errors but still in a suboptimal output regarding vertical alignment. For some reasons I cannot explain, but probably due to the way the tblr is constructed, this trick does not work for cells in the right column.

A solution, however, would be to wrap the \fillwithdottedlines macro in a \parbox, for example using \parbox{\linewidth}{\fillwithdottedlines{2cm} }. Take care of the required space before the last closing curly brace!

\documentclass[12pt]{article} \usepackage[a4paper, total={180mm,257mm}, left=15mm, top=20mm]{geometry} \usepackage{tabularray} \makeatletter \newlength\dottedlinefillheight \setlength\dottedlinefillheight{9mm} \def\fillwithdottedlines#1 {% \begingroup \ifhmode \par \fi \hrule height \z@ \nobreak \setbox0=\hbox to \hsize{\hskip \@totalleftmargin \vrule height \dottedlinefillheight depth \z@ width \z@ \dotfill}% \cleaders \copy0 \vskip #1 \hbox{}% \endgroup } \makeatother \begin{document} \begin{tblr}{ colspec = { Q[0.5\linewidth-5pt, c] X[c] }, row{1,2} = {1cm, m}, row{3} = {15cm, m}, vlines, hlines, } \SetCell[c=2]{c} \large \textbf{TITLE} \\ \textbf{Subtitle 1} & \textbf{Subtitle 2} \\ & \\ \parbox{\linewidth}{\fillwithdottedlines{2cm} } & \parbox{\linewidth}{\fillwithdottedlines{2cm} } \\ \end{tblr} %\fillwithdottedlines{5cm} \end{document}