Breakable side by side tcolorbox

Question

My initial goal was to have a layout structure, where there comes blindtext, then tow textboxes side by side, then again blindetext and so on. I tried to put two minipages side by side, both with 0.5\textwidth, but unfortunately this does not do the task , since the minipages are not breakable. Now I encountered the tcolorboxpackage. It has an extra feature called side-by-side tcolorboxes, but those are never breakable. My current approach was to put two tcolorboxes side by side with the tcbraster environment. This works well until I assign the breakable property to both of the tcolorboxes.

My code

\section{A section}

\begin{tcbraster}[raster columns=2,raster equal height, nobeforeafter, boxrule=0pt,width=0.45\textwidth, colback=white]
\begin{tcolorbox}[breakable]
erste Spalte
\end{tcolorbox}
\begin{tcolorbox}
zweite Spalte
\end{tcolorbox}
\end{tcbraster}

produces this

while

\section{A section}

\begin{tcbraster}[raster columns=2,raster equal height, nobeforeafter, boxrule=0pt,width=0.45\textwidth, colback=white]
\begin{tcolorbox}[breakable]
erste Spalte
\end{tcolorbox}
\begin{tcolorbox}[breakable]
zweite Spalte
\end{tcolorbox}
\end{tcbraster}

produces this

But I want that both textboxes' text can flow over more than one page.

By the way: How do I get rid of the borderline?

Answer 1

Reading the question it seems to me that you are not looking for actual boxed boxes but just want to have text side by side while allowing for page breaks. paracol supports such features.

\documentclass{article}
\usepackage{paracol}
\usepackage{lipsum}
\begin{document}
\section{A section}
\lipsum[1-4]
\begin{paracol}{2}
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
\switchcolumn[1]
Many more lines of text. Many more lines of text.
Many more lines of text. Many more lines of text.
Many more lines of text. Many more lines of text.
Many more lines of text. Many more lines of text.
Many more lines of text. Many more lines of text.
Many more lines of text. Many more lines of text.
Many more lines of text. Many more lines of text.
Many more lines of text. Many more lines of text.
Many more lines of text. Many more lines of text.
Many more lines of text. Many more lines of text.
Many more lines of text. Many more lines of text.
Many more lines of text. Many more lines of text.
\end{paracol}
\lipsum[4]
\end{document}

You can combine this with tcolorbox, if needed.

\documentclass{article}
\usepackage{paracol}
\usepackage{lipsum}
\usepackage[breakable]{tcolorbox}
\begin{document}
\section{A section}
\lipsum[1-4]
\begin{paracol}{2}
\begin{tcolorbox}[breakable]
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
\end{tcolorbox}
\switchcolumn[1]
\begin{tcolorbox}[breakable]
Many more lines of text. Many more lines of text.
Many more lines of text. Many more lines of text.
Many more lines of text. Many more lines of text.
Many more lines of text. Many more lines of text.
Many more lines of text. Many more lines of text.
Many more lines of text. Many more lines of text.
Many more lines of text. Many more lines of text.
Many more lines of text. Many more lines of text.
Many more lines of text. Many more lines of text.
Many more lines of text. Many more lines of text.
Many more lines of text. Many more lines of text.
Many more lines of text. Many more lines of text.
\end{tcolorbox}
\end{paracol}
\lipsum[4]
\end{document}

If you want to keep these boxes, you probably want to change their layout.

As you say that they should be invisible, here is a way to achieve this.

\documentclass{article}
\usepackage{paracol}
\usepackage{lipsum}
\usepackage[breakable]{tcolorbox}
\newtcolorbox{invbox}[1][]{breakable,boxrule=0pt,colback=white,colframe=white,#1}
\begin{document}
\section{A section}
\lipsum[1-4]
\begin{paracol}{2}
\begin{invbox}
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
Many lines of text. Many lines of text.
\end{invbox}
\switchcolumn[1]
\begin{invbox}
Many more lines of text. Many more lines of text.
Many more lines of text. Many more lines of text.
Many more lines of text. Many more lines of text.
Many more lines of text. Many more lines of text.
Many more lines of text. Many more lines of text.
Many more lines of text. Many more lines of text.
Many more lines of text. Many more lines of text.
Many more lines of text. Many more lines of text.
Many more lines of text. Many more lines of text.
Many more lines of text. Many more lines of text.
Many more lines of text. Many more lines of text.
Many more lines of text. Many more lines of text.
\end{invbox}
\end{paracol}
\lipsum[4]
\end{document}

However, in this case I'd probably just go with the plain paracol solution and change some indents if needed.