How do I add a block element after the current line, without interrupting the paragraph?

Question

The multicols package does not support single-column floats, only the *-form floats. I use multicols, and I have block elements (tables, figures, etc.) I'd like to float to the top (usually) of single columns.

I am prepared to 'manually float' the objects. I can see where the column break is and thus what appears immediately before and immediately after the object I want to insert. How can I insert the block element without ending the paragraph?

I sense that wrapfig with a width of \linewidth (which can be placed 'between words' of a paragraph, retaining the line/paragraph ends correctly... it might interfere with hyphenation, but if I'm at this stage of manual tweaking I can change words to avoid the hyphenation) will be the answer, but I wonder if there's another or a better way.

Edit: I just realized a probably-related question regarding 'floating longtables'. Sometimes this data has tables that run longer than the text height. I could start them immediately (possibly ending a multicols environment) and let things pick up where they will, but it might be nice to be able to say "at the end of this page, add this block-containing-a-longtable". That is, I take responsibility for decision, and LaTeX 'just' enacts that decision.

MWE Starting Point:

\documentclass{article}
\usepackage{multicol}
\usepackage{lipsum}

\title{Test Document}
\author{me}
\begin{document}
\maketitle
\begin{multicols}{2}
\lipsum[1]
Nam dui ligula, fringilla a, euismod
sodales, sollicitudin vel, wisi. Morbi
auctor lorem non justo. Nam lacus
libero, pretium at, lobortis vitae, ul-
tricies et, tellus. Donec aliquet, tortor
sed accumsan bibendum, erat ligula
aliquet magna, vitae ornare odio metus
a mi. Morbi ac orci et nisl hendrerit
mollis. Suspendisse ut massa. Cras
nec ante. Pellentesque a nulla. Cum
sociis natoque penatibus et magnis dis
parturient montes, nascetur ridiculus
mus. Aliquam tincidunt urna. Nulla
ullamcorper vestibulum turpis. Pellen-
tesque cursus luctus mauris.

\section*{Column broke on `dis'}
If I insert a manual break I get an indent on the next line because
it is a new paragraph (and the `dis line' might end up not justified,
if it otherwise had space added to cause justification --- it doesn't
seem to be the case this time). I want to be able to, say, somewhere
around `natoque' insert an instruction that says ``after this line is
complete, put a picture here''.

Or, I suppose, immediately between `dis' and `parturient' somehow say
``put the table \emph{right here}, no kidding around''. I think
wrapfig does this, but I haven't used it before, and I'm not certain of
the interactions between multicol and a wrapfig where the width is the
full linewidth.

\bigskip\noindent
\lipsum[3]
\lipsum[4]
\end{multicols}
\end{document}

Answer 1

You can forcefully end the paragraph at "dis" while setting \parfillskip to 0pt (see Is there a tool that makes paragraphs into rectangles?), then insert your figure as a non-float using float's [H]ERE specification, and continue the paragraph using \noindent. Grouping of the \parfillskip setting will only affect the paragraph in question.

\documentclass{article}
\usepackage{multicol,float,graphicx}
\usepackage{lipsum}

\title{Test Document}
\author{me}

\begin{document}

\maketitle

\begin{multicols}{2}
\lipsum[1]
{\setlength{\parfillskip}{0pt}%
Nam dui ligula, fringilla a, euismod
sodales, sollicitudin vel, wisi. Morbi
auctor lorem non justo. Nam lacus
libero, pretium at, lobortis vitae, ul-
tricies et, tellus. Donec aliquet, tortor
sed accumsan bibendum, erat ligula
aliquet magna, vitae ornare odio metus
a mi. Morbi ac orci et nisl hendrerit
mollis. Suspendisse ut massa. Cras
nec ante. Pellentesque a nulla. Cum
sociis natoque penatibus et magnis dis}

\begin{figure}[H]
  \centering
  \includegraphics[width=\linewidth]{example-image}
  \caption{This is a figure caption.}
\end{figure}

\noindent
parturient montes, nascetur ridiculus
mus. Aliquam tincidunt urna. Nulla
ullamcorper vestibulum turpis. Pellen-
tesque cursus luctus mauris.

\section*{Column broke on `dis'}
If I insert a manual break I get an indent on the next line because
it is a new paragraph (and the `dis line' might end up not justified,
if it otherwise had space added to cause justification --- it doesn't
seem to be the case this time). I want to be able to, say, somewhere
around `natoque' insert an instruction that says ``after this line is
complete, put a picture here''.

Or, I suppose, immediately between `dis' and `parturient' somehow say
``put the table \emph{right here}, no kidding around''. I think
wrapfig does this, but I haven't used it before, and I'm not certain of
the interactions between multicol and a wrapfig where the width is the
full linewidth.

\bigskip\noindent
\lipsum[3]
\lipsum[4]
\end{multicols}

\end{document}