pgfplots: Weird problem when using `\addlegendentry` with line break

[Manuel Kuehner]

See https://tex.stackexchange.com/questions/636298 (incl. screenshot)

• I want to have an additional multi-line custom entry in the legend (\addlegendentry).
• Therefore, I follow https://tex.stackexchange.com/questions/204395/.
• I also want the legend to be left-aligned.
• Somehow, I need both (seemingly redundant) following lines to make it work:

---

legend style = {
	cells = {align = left}, % When commented out then error occurs
	},			
legend cell align = {left},	

---

• If I remove cells = {align = left}, the I get an error.
• If I remove legend cell align = {left}, then the alignment is centered.

\documentclass[12pt,letterpaper,landscape]{article}

\usepackage{mathtools}

\usepackage{pgfplots}
\pgfplotsset{compat=1.18}

\begin{document}

\begin{tikzpicture}
    \begin{axis}[
    legend style = {
        cells = {align = left}, % When commented out then error occurs
        },          
    legend cell align = {left},     
    ]
    % Plot A
    \addplot{x^2 - x + 4};
    \addlegendentry{$T_\text{R, I}$}
    % ---
    % https://tex.stackexchange.com/questions/204395/
    \addlegendimage{empty legend}
    \addlegendentry{
        Line 1\\
        Line 2
        }   
    \end{axis}
\end{tikzpicture}

\end{document}

[Mo-Gul]

See my answer to your question on TeX.SX.