First: I've split up my question(s) from Cleaning up code and here is one of the bullets, with the code somewhat reduced.
Consider
\DocumentMetadata{} \documentclass[ a4paper, 12pt ]{article} \usepackage[ hmargin = 2.3cm, vmargin = 3cm ]{geometry} \usepackage{multirow,array} \def\mlr{1} \newcommand*\saenk[1]{\raisebox{\fpeval{-5/9*\mlr}ex}{#1}} \begin{document} \begin{center} \begin{tabular}{ |p{5cm}| >{\centering\arraybackslash}p{5cm}| >{\centering\arraybackslash}p{5cm}| } \hline \multicolumn{1}{|c|}{\multirow{2}{*}{\raisebox{\fpeval{-1.5*\mlr}ex}{Du kender \dots}}} & \multicolumn{2}{ c|}{\saenk{Du kan beregne \dots}} \\[\mlr ex] \cline{2-3} & \saenk{sider} & \saenk{vinkler} \\[\mlr ex] \hline A & B & C \\ \hline \end{tabular} \end{center} \end{document} Question
How do I color the cell background of the header of the table, i.e., the cells with the text Du kender \dots, Du kan beregne \dots, sider and vinkler? That is (probably), how can I use colortbl with this code?
colortblpackage, which is the standard way of coloring table cells/rows/columns - you have most likely also encountered this package when doing research for your question. However, when just loading the package (and not using any of its commands yet) I got aMisplaced \omiterror. So I guess the question essentially is "how can I usecolortblwith this code?" Maybe you can edit to reflect this.:-)However, I would like to be able to achieve all three bullets in the referenced question at the top of the question.